As President Putin moves to annex Crimea, US vice-president Joe Biden arrives in Poland "to confirm NATO obligations" and consult on measures to support Ukraine's sovereignty.
Joe Biden arrived in Warsaw on Tuesday morning for talks with Polish prime minister Donald Tusk, President Bronislaw Komorowski and Estonian president Toomas Hendrik Ilves on the deteriorating situation in eastern Ukraine.
A statement by the American Embassy in Warsaw says the vice-president "will meet with regional partners to discuss events in Ukraine and other issues" and "will consult on measures to support the sovereignty and territorial integrity of Ukraine" and confirm NATO defence commitments.
As Biden has talks with leaders of countries on Russia's western border, President Vladimir Putin informed Russia's parliament formally on Tuesday of Crimea's request to join the country, the first legislative step towards absorbing the peninsula following Sunday's referendum where 97 percent said they wanted to leave Ukraine and join the Russian Federation.
Crimea was transferred from Russia to Ukraine while under Soviet rule in 1954 following Stalin's death the year before and much of its population is ethnic Russian or Russian speaking.
The EU and US have declared the referendum illegal and imposed travel restrictions and asset freezes on Monday against Russian and Ukraine officials.
"Our joint position is clear: there can be no acceptance of violations against Ukraine's independence or its territorial integrity," Prime Minister Donald Tusk said ahead of Biden's visit.
On the comparatively mild sanctions by the EU and US against Russia, Tusk warned: "Those calling for tougher sanctions must be aware of what they are calling for," he said at the prospect of retaliation by the Kremlin.
"Fortunately there is a space between war and capitulation," he added.
US F-16 fighters of the 555th Fighter Squadron from the Aviano Base, Italy, have been arriving at Poland's Lask air base to augment the US military’s presence in the region.
Meanwhile, the UK's defence minister announced on Monday that Britain will send six Eurofighter Typhoon jets to the Baltic region in late April.
According to newspaper Lithuania Tribune, the six jets will be added to the scheduled rotation by the Polish air force to protect former Soviet states of Lithuania, Latvia and Estonia against any military threat from Russia. (pg)