By Kathleen Hennessey and Christi Parsons, Tribune Washington Bureau

WASHINGTON — Two and a half years after President Barack Obama vowed to shift America’s diplomatic, economic and military focus to Asia, he will head back to the region this week to try to convince allies and adversaries alike that he really meant it.

Since the much-touted decision to “pivot” to Asia, the Obama administration has found itself repeatedly pulled away by crises in the Middle East, political battles in Washington and, more recently, turmoil in Ukraine.

A key piece of the policy, an ambitious Pacific Rim free-trade pact, has met resistance from the president’s own party and bogged down in tariff disputes with Japan. The promised transfer of U.S. warships, Marines and other military resources to the Pacific has been incremental, and limited by Pentagon budget cuts.

The result is anxiety among allies, and questions about the U.S. commitment to establishing a counterweight to China’s growing economic clout and military assertiveness.

“In polite company people won’t say it, but behind closed doors I think they’ll openly ask where the pivot is,” Victor Cha, former director for Asian affairs in the George W. Bush administration, said at a recent forum at the nonpartisan Center for Strategic and International Studies.

Starting Wednesday, Obama will aim to answer that question at stops in Japan, South Korea, Malaysia and the Philippines. White House advisers say the U.S. remains locked into plans to bolster its military presence, to beef up bilateral relations and regional alliances, and to complete the 12-nation Trans-Pacific Partnership trade talks.

Susan Rice, Obama’s national security adviser, portrayed the president’s fifth trip to Asia as crucial to America’s future.

“We increasingly see our top priorities as tied to Asia, whether it’s accessing new markets or promoting exports or protecting our security interests and promoting our core values,” she said at a White House briefing Friday.

“There’s a significant demand for U.S. leadership in that region,” she said.

Outside experts don’t expect Obama to make major promises or offer new resources in six days of official dinners, speeches and “cultural visits,” including one to the National Mosque in Malaysia’s capital, Kuala Lumpur.

He may not even mention the word “pivot.” White House aides now cite a “rebalance” in part because U.S. allies in Europe and the Middle East complained that a pivot suggested they were a lower priority.

The promise to increase U.S. engagement took a hit last fall when Obama scrubbed a trip to Asia, and his participation in two regional summits, because of the 16-day government shutdown. Since then, Russia’s annexation of Crimea from Ukraine has rattled nerves in Asia, where some see parallels to China’s claims to disputed islands and shoals in the South and East China seas.

“Obama’s canceled visit in October, although for good reason, will see him return to a very different circumstance in Asia,” said Simon Tay, chairman of the Singapore Institute of International Affairs. “While he will still be greeted with much fanfare … the truth is that the region has moved on.”

Two key U.S. allies, Japan and South Korea, are bickering over a host of issues, even as they face increased tension with North Korea. The Philippines has locked horns with China, and no one is happy about Malaysia’s bungling in the search for Flight 370, which disappeared more than a month ago.

“The good thing is that Chinese actions still cause tensions, and so even if the Americans aren’t loved, they seem needed,” Tay said.

Obama will be careful not to take sides in the territorial disputes or to directly antagonize leaders in Beijing. Obama’s aides have denied that America’s new emphasis on Asia is designed to encircle China or restrain its initiatives, but Chinese authorities are suspicious.

In the briefing Friday, Rice denied that the trip, or the policy, “ought to be viewed as a containment of China.”

“The idea here is to have the U.S. shape the security environment, not be drawn into a conversation with China,” said Kenneth Lieberthal, an Asia policy expert at the Brookings Institution. Obama must show support for allies without “making China the bull’s-eye.”

The president’s visit will be his third since he and then-Secretary of State Hillary Rodham Clinton outlined a lofty vision in the fall of 2011. America would move away from the long, costly wars in Iraq and Afghanistan, and into what Clinton dubbed “America’s Pacific century.”

At the time, Obama suggested that America’s new commitment would be symbolized by the posting of 2,500 Marines to Darwin in northern Australia. About 1,500 Marines are now there, but the rest won’t arrive until 2016.

In a report released last week, the Senate Foreign Relations Committee concluded that the pivot has fallen short.

“Despite progress in some areas, implementation of the rebalance thus far has been uneven, creating the risk that the rebalance may well end up as less than the sum of its parts,” said committee chairman Sen. Robert Menendez, D-N.J.

The committee found that State Department efforts have lagged behind those of the Pentagon. In Manila, for example, Obama is expected to sign an agreement expanding U.S. access to a Philippine military base, a sign of the gradually improved military cooperation since Philippine lawmakers in 1991 forced America’s massive air and naval bases to close.

But Defense officials say they’ve struggled to make good on the president’s vision with a shrinking budget.

In March, one Defense official said bluntly that the pivot “can’t happen,” a comment she later took back. In January, Gen. Herbert “Hawk” Carlisle, commander of U.S. Pacific Air Forces, told Defense News that budget cuts had made it “incredibly hard” to shift resources to the Pacific.

Progress on trade appears equally difficult. Japanese and U.S. trade negotiators intensified talks in recent weeks in hopes of giving Obama and Prime Minister Shinzo Abe good news to announce during the state visit to Tokyo.

But disputes over agricultural and automobile tariffs have lowered expectations. One official said the two leaders would claim only progress, not a deal.

Some critics cite another factor undermining the rebalance: Obama’s credibility problem.

Allies in Asia took note when Obama battled unsuccessfully to block automatic budget cuts from taking effect, and he has not persuaded fellow Democrats to fast-track a vote on the Pacific Rim trade deal.

Some experts said Obama’s threats last summer to launch punitive airstrikes against Syria after chemical weapons were used, his subsequent decision to seek congressional approval and his inability to get it, have sapped confidence in his leadership.