Vice President Joe Biden told Ukraine's new prime minister Thursday that the U.S. welcomes the formation of the country's new government.

Biden's message was an important signal of U.S. recognition for Arsenij Yatsenyuk, named to the post Thursday in a boisterous parliamentary session, as the de facto leader of the former Soviet republic. Biden called Yatsenyuk to tell him the U.S. will give full support as Ukraine seeks to restore order in the wake of a major political crisis.

The White House has said by fleeing the capital, President Viktor Yanukovych abdicated power, but he reportedly still claims authority. Biden had spoken to him regularly during the crisis until he fled.

Yatsenyuk was overwhelmingly approved by parliament Thursday. He's widely viewed as a technocratic reformer and has said Ukraine's future lies with the European Union.

Earlier Thursday, Secretary of State John Kerry said that Russia has told the United States that it will respect the sovereignty of Ukraine and that military exercises near the Russian-Ukraine border are not a prelude to an intervention.

Russia scrambled fighter jets to patrol its border and reportedly gave shelter to Ukraine's fugitive president. But Russian Foreign Minister Sergei Lavrov assured Kerry the buildup was scheduled previously and was unrelated to the recent unrest in Ukraine.

The military movements had unnerved the U.S. because they followed the overthrow of Yanukovych, who has fled Kiev, the capital, and reportedly is seeking refuge outside Moscow.

Kerry warned Russia this week against a military intervention the former Soviet republic and said it could face a strong response from the West, though he did not specify what that might be.

"We will look to Russia for the choices that it makes in the next days for their confirmation of these statements," Kerry said at a State Department news conference with German Foreign Minister Frank-Walter Steinmeier. "Words are words. We have all learned that it's actions and the follow-on choices that make the greatest difference."

Kerry predicted that the military exercise will not be "so prolonged that it is going to have an impact on events there."

"Everybody needs to step back and avoid provocations," Kerry said.

Kerry said the U.S. also supports a vote Thursday by Ukraine's parliament to approve the transitional government that will run the country until elections in May. But in Ukraine's strategic Crimea region, gunmen stormed government buildings and raised a Russian flag over the regional parliament.

Moscow is "concerned" about the takeover in Crimea, and Kerry said Lavrov "disclaimed that it had anything to do with any formal Russian initiative."

"They don't want to see a breakdown into violence," Kerry said. Even so, he struck a skeptical tone, noting that Russia can't credibly claim to protect Ukraine's territorial integrity if it is also encouraging a separatist movement.

"Nowhere is there a greater connection, a link to Russia in several different ways as there is in Crimea," Kerry told reporters. "But as the days unfold this should not become a struggle between the United States and Russia, East and West. This is about the people of Ukraine."

Yanukovych reportedly is still claiming authority as Ukraine's president. But Kerry said "it is clear that events have now overtaken whatever legitimacy he claimed." White House press secretary Jay Carney echoed that view, contending Yanukovych "abdicated his responsibility" and left a "void" that Ukraine's lawmakers are trying to fill.

Carney said the U.S. expects the interim government to protect the security and civil rights of all of citizens in Ukraine, which has a large Russian-speaking population.

Steinmeier said it's important for Kiev's new leaders to "show that it is a government for all Ukrainians and that it now works together with international institutions, and with its neighbors, to stabilize the country financially."

"East and West should not argue now about Ukraine's future," he said.

In a statement before the news conference, Steinmeier said welcomed a move by the International Monetary Fund to send a fact-finding team to Kiev. He said he will discuss with IMF chief Christine Lagarde on Friday what the financial institution can do in terms of providing immediate aid.

"We are talking with Russia about help pledged to Ukraine not being withdrawn or canceled," he said.

Kerry was asked if the Ukraine should be integrated into the European Union and NATO -- a possibility that has strong backing in Kiev and sparked protests against Yanukovych. Kerry said he would advise the new government to hold off and "focus on the things that need to be focused on now."