Right before President Donald Trump unveiled punitive measures against China on May 29, he inserted a surprise into his prepared text.

“We will be today terminating our relationship with the World Health Organization," he announced during a press conference in the Rose Garden.

Most of the president's top aides — and even some of his Cabinet secretaries — were blindsided.

Just 11 days earlier, Trump had sent an ultimatum threatening to withdraw from the WHO if reforms were not enacted in 30 days. Some senior officials hoped that he was bluffing or would change his mind about a decision that could hobble efforts to fight dangerous diseases.

Trump's foreign policy choices are at the center of a forthcoming book by former national security adviser John Bolton, who argues that many of the president's erratic actions are aimed at boosting his re-election chances.

But while Bolton's book focuses on revelations about Trump's past dealings with Turkey, Ukraine and China's leader Xi Jinping, officials interviewed by ProPublica said the less explored WHO decision may have a more lasting impact.

ProPublica has interviewed senior officials at five federal agencies to understand the repercussions and the behind-the-scenes efforts to contain the damage of a decision in which they had little input.

In the weeks after Trump's Rose Garden declaration, the White House gave little direction on what to do next. Officials who deal with the WHO knew that withdrawal is a cumbersome process requiring a year's notice, a multiagency review and payment of unpaid dues.

As a result, Health and Human Services Secretary Alex Azar instructed his department to continue cooperating with the organization. The American ambassador in Geneva, Andrew Bremberg, kept negotiating with the WHO director general on the reforms demanded by the president, including an independent inquiry into the WHO's response to the pandemic. (The talks were first reported by Vanity Fair.) Dozens of scientists, doctors and public health specialists detailed from the Centers for Disease Control and Prevention kept working at their posts at the WHO's Geneva headquarters and in the field, fighting Ebola and other diseases in Africa and elsewhere.

But on Monday, the administration made it clear there would be no backing down.

At a meeting at the White House, a director with the National Security Council told diplomats and health officials that they must now justify any engagement with the WHO as being necessary for national security and public health safety, senior government officials told ProPublica. In addition, the State Department has begun preparing formal paperwork to declare the official withdrawal of the United States from the WHO, officials said.

“The president is moving toward a fast withdrawal," a senior administration official said in an interview this week. Another administration official said on Friday that the White House does not plan to reconsider the decision. National security and health officials confirmed those assertions.

“The President has made clear that the U.S. is terminating its relationship with the World Health Organization, and that process is being expedited," said Katie McKeogh, an HHS spokesperson, in an email response to a request for comment. “All US-WHO collaborations are being examined through an interagency exercise as part of the termination process to ensure the safety of the American people will be protected."

The new “no-engagement" policy is a concrete step to curtail the relationship, and it has caused alarm and confusion, other officials said.

“This is sending just unbelievable shock waves through the agencies," a senior government official said. The official warned that reduced cooperation with the WHO will have “profound and severe repercussions."

Among the most immediate potential impacts: The move could for the first time cut the U.S. government out of the development of the seasonal influenza vaccine for the Southern Hemisphere, a process coordinated by the WHO in partnership with the United States. And the withdrawal from the WHO could impede access to an eventual COVID-19 vaccine if it is created overseas, current and former officials said.

Leaving the organization could also significantly blind the U.S. to health threats in remote foreign locales that, as the pandemic has shown, have the potential to make their way to the U.S. shores. Experts also fear the impact on major initiatives to combat infectious diseases, such as a WHO-led program that is on the cusp of eradicating polio.

“To do this in the middle of a pandemic is breathtakingly dangerous," said Nancy Cox, a former CDC virologist, who for 22 years led the agency's WHO center on influenza surveillance and control. “So I worry a lot about what's going to happen to so many of the programs at WHO that were strongly supported financially and through expertise and consultation with the U.S. I just think it could be really bad."

When informed of the NSC directive, a WHO spokesman in Geneva wrote that the organization “hopes the United States will remain part of WHO, as it has been since 1948. Its leadership in global public health as a WHO Member State is important to all people, everywhere."

The United States is the largest donor among the WHO's 194 member states, giving about $450 million last year. The WHO said the U.S. cut in funding would affect childhood immunizations, polio eradication and other initiatives in some of the most vulnerable parts of the world.

Trump's disgust with the WHO is well-founded, administration officials say. The decision to leave wasn't solely due to the WHO's stumbles on COVID-19, but because they capped a record of unresolved structural issues and failures during crises, officials said. As the pandemic spread early this year, the WHO reported that only 1% of cases were asymptomatic, while Chinese doctors were privately saying that the number was actually as high as 50%, the senior administration official said.

“The organization had no credibility," the official said. “It was either clueless or cut out, being manipulated."

Recent missteps, including conflicting advice about the efficacy of masks, raised further questions, officials said.

The administration plans to fill the void left by its withdrawal with direct aid to foreign countries, creating a new entity based in the State Department to lead the response to outbreaks, according to interviews and a proposal prepared by the department. The U.S. will spend about $20 billion this year on global public health. (About $9 billion of that is emergency aid for COVID response.)

But the senior administration official conceded that important activities led by the WHO, including vaccination initiatives, need to continue. It is not yet clear what will happen to those programs when American funding and participation end, the official acknowledged.

In fact, many aspects of the new policy toward the WHO remain unclear, officials said. At the White House meeting Monday, the NSC director who outlined the policy did not answer a number of questions from the agencies about its implementation and impact, saying responses would come later, the senior government official said.

The new directive will require officials to divert their attention from pandemic response in order to review a list of their WHO-related activities and try to justify them on national security and public health safety grounds, the senior government official said.

Critics warn of potential widespread damage as the United States attempts to extricate itself from an international health infrastructure in which it is entrenched. The timing will cause even more uncertainty, they said.

A case in point: The flu vaccine that Americans receive at drugstores and doctors' offices is based on work that the CDC and Food and Drug Administration conduct through the WHO.

Since 2004, the U.S. has helped build a global network of WHO flu centers, buying lab equipment and training scientists. The centers in more than 100 countries collect samples from sick people, isolate the viruses and search for any new viruses that could cause an epidemic or pandemic. The CDC houses one of five WHO Collaborating Centers that collect these virus samples, sequence the viral RNA and analyze reams of data on flu cases around the world, while the FDA runs one of the four WHO regulatory labs that help vaccine makers determine the correct amount of antigen, which triggers the immune response, to include in vaccines.

The U.S. and other WHO members meet twice a year to pick the dominant flu viruses that are included in vaccines. The strains for this fall's flu vaccine in the U.S. were chosen in April. But in September, the WHO flu centers are scheduled to pick the flu strains for the Southern Hemisphere's vaccine, and months of work at the CDC leads up to that meeting.

The uncertainty has caused concern in the pharmaceutical industry as well as the government, officials said. The CDC could lose access to the data and virus samples that protects Americans from potentially deadly strains of flu from around the world.

“If we pull out of the World Health Organization, we're going to be flying blind in terms of influenza and other pandemic threats," said Cox, the CDC flu expert, who retired in 2014. “It's going to be a lot harder to know what's going on."

The onslaught of the coronavirus has hurt immunization activities worldwide, causing a rise in measles and other diseases. American cooperation with the WHO is vital to fighting such threats, according to current and former officials. They fear that the U.S. decision will endanger a WHO-led program that has come tantalizingly close to the eradication of polio. The wild form of the disease now lingers in just two countries, Pakistan and Afghanistan.

“We are using WHO to run an anti-polio campaign and coordinate it," said Andrew Natsios, a former administrator of the U.S. Agency for International Development and director of the Scowcroft Institute of International Affairs at Texas A&M University. “And we're almost there. We can't stop that now."

The Trump administration's plan to bypass the WHO and address global health problems directly with foreign governments will run into trouble in the Middle East, South Asia, Africa and other regions where Americans encounter hostility or have difficulty operating, critics said.

“People coming into countries in WHO shirts to work on polio or AIDS are less threatening," said former Ambassador Jimmy Kolker, a veteran health diplomat who represented the United States at WHO meetings until 2017. “It is easier to get collaboration from a skeptical country or population through WHO. It facilitates access."

It is fanciful to think that other nations will accept a U.S.-led health initiative as a substitute for the WHO, Kolker said.

“No one is looking for U.S.-based alternatives to WHO," he said. “Dead on arrival. There is no way they are going to be supported or even accepted."

The WHO has a history of bringing together ideological rivals. William Foege, a CDC director under Presidents Ronald Reagan and Jimmy Carter, credits the global agency for uniting American scientists and their counterparts from the Soviet Union during the Cold War to eradicate smallpox in a little more than a decade.

“It's not a failed bureaucracy," said Foege, who worked on the international fight against smallpox. “If you go there and see all they do every year, and they have a budget for the entire world that's smaller than many medical centers in this country."

At the same time, global health experts across the political spectrum admit that the WHO needs reform. The organization does not have the muscle to enforce international health regulations or put pressure on member states, experts say. Its decentralized structure gives the headquarters in Geneva limited power over regional offices, some of which have been fiefs dominated by politics and patronage.

During the U.S. response to the Ebola outbreak in West Africa in 2014, the Obama administration's displeasure with the WHO led American officials to bypass the agency and join forces instead with other nations and nongovernmental organizations, current and former officials said.

The WHO's flawed record shows the need for the United States to take the lead in response to health crises, a senior administration official said.

“As U.S. leadership demonstrated in the Ebola and MERS outbreaks, our diplomatic and development efforts enable countries to develop tools for addressing infectious disease," the official said. “Due to these efforts, we filled gaps created by the WHO's inaction to prevent, detect and respond to outbreaks immediately."

Kolker said the calls for reform are legitimate, but he and others said the United States has enough influence to make changes from within. They disagree with the allegations that China controls the WHO and its director general, Tedros Adhanom Ghebreyesus.

“In general, the WHO is deferential to member states," Kolker said. “Yes, it should have been more aggressive in response to Chinese obstruction. Tedros surely realizes the public statements were too deferential to China. But the organization is not dominated by China. Its weaknesses reflect the challenges we have long faced in international collaboration on public health."

China will gain control over the organization if Washington really does terminate its membership, current and former officials predicted.

“There's one country that's desperate for the United States to leave the WHO, and that's China," Sen. Chris Murphy, a Connecticut Democrat, said at a hearing Thursday of the U.S. Senate Committee on Foreign Relations. “They are going to fill this vacuum. They are going to put in the money that we have withdrawn, and even if we try to rejoin in 2021, it's going to be under fundamentally different terms because China will be much more influential because of our even temporary absence from it."