US Vice President Joe Biden arrived in Poland for talks with regional allies Tuesday as Russia tightened its grip on the Ukraine's breakaway region of Crimea.
Biden will hold talks with Polish President Bronislaw Komorowski and Prime Minister Donald Tusk, as well as the presidents of Estonia, Latvia and Lithuania -- meeting the latter two in Vilnius on Wednesday.
The White House has said the talks will focus on "steps to support Ukraine's sovereignty and territorial integrity, and affirm our collective defence commitments under the North Atlantic Treaty".
Lithuanian Prime Minister Algirdas Butkevicius said Biden's visit was "a clear signal to those who are interested in destabilising the situation in the region".
"We see his visit as yet further proof that NATO allies, and notably the US, are keeping up their commitment to collective defence," he told Lithuanian national radio.
The events in Crimea have rattled nerves in Poland and the three Baltic states, which were all under Moscow's thumb before the collapse of the Soviet Union in 1991.