By Sergei L. Loiko, Los Angeles Times

KIEV, Ukraine — The United States will stand by Ukrainians against Russian aggression that threatens their nation’s sovereignty and territorial integrity, Vice President Joe Biden pledged Tuesday during a visit to Kiev.

“No nation has the right to simply grab land from another nation, and we will never recognize Russia’s illegal occupation of Crimea, and neither will the world,” Biden said after meeting with Ukraine’s acting prime minister, Arseny Yatsenyuk. “No nation should threaten its neighbors by amassing troops along the border. We call on Russia to pull back these forces. No nation should stir instability in its neighbor’s country.”

Biden threatened greater costs and greater isolation for Russia, already facing fresh sanctions after annexing Crimea last month, and demanded that it “stop supporting men hiding behind masks in unmarked uniforms sowing unrest in eastern Ukraine.”

“I came here to Kiev to let you know, Mr. Prime Minister, and every Ukrainian know that the United States stands with you and is working to support all Ukrainians seeking a better future,” Biden said. “You should know that you will not walk this road alone. We will walk it with you.”

He accused Russia of failing to abide by commitments to help de-escalate the situation in eastern Ukraine made last week during meetings with officials from the United States, Ukraine and the European Union.

“Now it is time for Russia to stop talking and to start acting on the commitments that they made to get pro-Russia separatists to vacate buildings and checkpoints, accept the amnesty,” Biden said. “That is not a hard thing to do. … We need to see this kind of concrete steps, we need to see them without delay.”

Biden pledged that the United States would provide nonlethal military aid to Ukraine. He also noted that the United States had committed to providing a $1 billion loan guarantee to help shore up the interim government in Kiev, which took power in February with the fall of pro-Russian President Viktor Yanukovich.

Armed separatists that Ukraine and many in the West maintain are coordinated and led by Russian agents continued to hold administrative buildings in several key cities and towns of eastern Ukraine. The sites included an administrative building in Donetsk, the coal-mining region’s center, and the Security Service station in Luhansk, the industrial capital of a neighboring district.

In the north of the Donetsk region armed militants have full control of the towns of Kramatorsk and Slovyansk. In Slovyansk, gunmen allegedly led by a Russian commando on Tuesday demanded additional firearms in exchange for a local police chief they had kidnapped the previous day, UNIAN news agency reported.

The separatists have insisted they won’t disarm until the interim government in Kiev does the same, calling its rule of Ukraine the result of an illegal coup.

The government Tuesday submitted a bill to Parliament that offered amnesty for separatists who surrender seized buildings and give up arms, said a Foreign Ministry statement posted on its official website.

Biden commended that measure as a sign that Ukraine will fulfill commitments made in Geneva, including holding elections next month that “are clean and closely monitored so that nobody on the 26th of May can question their legitimacy.”

“I am genuinely encouraged to see so many people in the east rejecting guns and choosing the ballot box to determine Ukraine’s future,” he said.

Biden also met Tuesday with acting President Oleksandr Turchynov, who pledged that Ukraine’s interim government would do its best to hold an “honest and transparent presidential election,” a statement on Parliament’s official website said.

For his part, Yatsenyuk charged that Russia was seeking to disrupt the coming elections.

“Ukraine needs a legitimately elected president, something Russia doesn’t want,” the acting prime minister said after his meeting with Biden, demanding that the Russians “abide by their international commitments” and “not behave like gangsters.”

In sending one of its top politicians to embattled Ukraine, the United States delivered a clear message to Russia to keep it hands off its neighbor, Ukrainian political scientist Vadim Karasyov said.

“Biden made it more than clear today that the United States will not give Ukraine away to Russia,” Karasyov, head of Kiev-based Institute of Global Strategies, said in an interview. “The most important point Biden made today was a pledge to see to it that the presidential election will be held in Ukraine on time, regardless of Russia’s aggressive meddling.”

“The message Biden voiced today boils down to the fact that Ukraine and the United States have entered special strategic relations which will help Ukraine develop as a united, free and democratic state,” Karasyov said.

As Biden was leaving his Kiev hotel Tuesday morning a hotel manager asked him to sign a guest book, the vice president said, adding: “I signed: Ukraine united, Joe Biden.”

Olivier Douliery/Abaca Press/MCT