(Clarifies analyst comment in paragraph 13)
* Eastern Europeans anxious after Russia action in Crimea
* Biden to discuss NATO support, energy security
* U.S. vice president is starting two-day mission in Warsaw
By Roberta Rampton
WARSAW, March 18 (Reuters) - U.S. Vice President Joe Biden landed in Warsaw on Tuesday on a mission to reassure allies in eastern Europe that Washington understands their anxieties about Russia's actions in Ukraine and will protect them if needed, officials said.
The countries have become increasingly nervous that they could be next in line to face aggression from Russia after President Vladimir Putin's interventions to annex Ukraine's Crimea region.
On the two-day mission, Biden plans to discuss ways to help the region become less dependent on Russian oil and gas and limit Moscow's ability to use its energy supplies for political leverage, a senior administration official said.
He will also talk about new ways NATO and the United States could support their allies, building on U.S. participation last week in war games in Poland and increased fighter jet patrols in the Baltics.
"He will be talking about further steps that the United States can take and that NATO can take as an alliance to further ensure the security of Poland and the Baltics and other NATO alliances," the official told reporters travelling with Biden.
"They'll discuss energy security, and including in that, long-term diversification of energy supply, so that energy can't be used as a political tool," the official said, citing shale gas and nuclear power as two areas for discussion.
The United States is poised to become a major exporter of liquefied natural gas in coming years, making inroads into a market that Russia currently dominates.
Natural gas importers from around the world have urged the Obama administration to speed up approvals of additional export facilities so they can become less reliant on Russia.
On Tuesday, Biden is scheduled to meet with Polish Prime Minister Donald Tusk and President Bronislaw Komorowski. He will also hold talks with Estonian President Toomas Hendrik Ilves, who is in Warsaw on an official visit.
On Wednesday in Vilnius, Biden will meet with Lithuanian President Dalia Grybauskaite and Latvian President Andris Berzins.
NATO's top military commander, U.S. Air Force General Philip Breedlove, also is slated to meet with chiefs of defence in central and eastern Europe to discuss security issues this week, the official said.
Biden's trip will serve to underscore to the leaders, as well as to countries like the Czech Republic and Hungary, that "we've got their back", said Julianne Smith, a former deputy national security adviser to Biden, in an interview before the trip.
The message is also aimed partly at Russia, warning Putin to think twice before messing with NATO allies, said Smith, now with the Center for a New American Security think-tank in Washington.
Biden also wants to get an assessment from leaders about the impact of sanctions imposed this week by the United States and European Union, the senior administration official told Reuters.
As neighbours of Russia, with close economic ties, retaliation for sanctions could be an issue.
"He's going to hear an earful," said Heather Conley of the Center for Strategic and International Studies (CSIS) in Washington.
For Poland and the Baltics, which like Ukraine, were formerly part of the Soviet Union, watching the Crimean crisis unfold is a "nightmare scenario", Conley said in an interview.
Early in his presidency, Obama scaled back plans for missile defence systems based in eastern Europe, adding to anxieties for neighbours of Russia.
But there is no consideration being given to changing those plans, the senior administration official told reporters. (Editing by Christian Lowe and Andrew Heavens)