U.S. Vice President Joe Biden on Tuesday condemned Russia's annexation of Ukraine's Crimean peninsula, saying European borders "should never again be changed at the point of a gun."
Biden spoke at a military base near the Romanian capital, Bucharest, to U.S. and Romanian troops, as part of a U.S. push to reassure NATO allies of strong U.S. support. He described the Russian annexation as "an illegal occupation of Crimea," and called on NATO countries to "remain resolute in imposing greater costs on Russia" for its actions.
As pro-Russian separatist unrest continues to grip eastern Ukraine, Moscow has again insisted that tens of thousands of its troops massed near the Ukraine border have begun to withdraw.
The Kremlin has touted the withdrawal for the past two weeks, but the NATO command says it has not yet seen evidence of the pullback.
Washington and its NATO allies have repeatedly accused Moscow of using the troop deployment to intimidate the Kyiv government, as Ukraine prepares for presidential elections set for Sunday.
Pro-Russian gunmen sit on an armored personnel carrier with the words read "Battalion Vostok (East) " as they patrol in Donetsk, Ukraine, May 20, 2014.
Coal miners sit on a bus after finishing their shift at a coal mine outside Donetsk, Ukraine, May 20, 2014.
Vyacheslav Ponomarev, the self-proclaimed mayor of Slovyansk, speaks to citizens whose homes were ruined by shelling in Slovyansk, eastern Ukraine, May 20, 2014.
Yekaterina Len cries inside the remains of her house damaged by shelling as her grandson stands near her, in Slovyansk, eastern Ukraine, May 20, 2014.
Presidential candidate Petro Poroshenko meets with supporters in the Cherkasy region, central Ukraine, May 20, 2014.
A pro-Russian militant defends a front line position with a machine gun, Slovyansk, Ukraine, May 19, 2014.
Residents watch the flames from a damaged gas pipe that was hit by a mortar bomb, during fighting between Ukrainian government troops and pro-Russian militants, outside Slovyansk, Ukraine, May 19, 2014.
Pro-Russian militants detain three men they suspect of spying for the Ukrainian government in Kramatorsk, eastern Ukraine, May 18, 2014.
A pro-Ukrainian activist prepares to hoist the Ukrainian flag in the town of Velika Novosyolka, in the Donetsk region, eastern Ukraine, May 17, 2014.
A masked pro-Russian militant stands behind the barricades at a checkpoint blocking the major highway outside Kharkiv, eastern Ukraine, May 17, 2014.
Despite those accusations of meddling, Russian Deputy Foreign Minister Grigory Karasin said he believes the Ukraine poll will deepen the country's political divisions if hostilities continue in eastern Ukraine. He also voiced concern about Kyiv's military push to regain control of buildings in eastern Ukraine seized in recent weeks by pro-Russian separatists.
Separatist leaders in the Donetsk and Luhansk regions insist the presidential poll will not be held in those territories, where the United Nations refugee agency says 10,000 civilians have so far been displaced. A U.N. statement Tuesday said that number continues to rise.
Meanwhile, thousands of people in several eastern Ukrainian cities attended peace rallies against pro-Russian separatists called by one of the country's richest men, Rinat Akhmetov. The metals tycoon accused the pro-Russian rebels of looting and "fighting against the citizens" of the region.
In response to Akhmetov, pro-Russian separatist leader Denis Pushilin announced that the so-called Donetsk People's Republic will begin nationalizing the assets of "regional oligarchs" who refuse to pay taxes to the self-declared breakaway state.
The United States and its European allies have warned Moscow that they will impose new sanctions against key sectors of Russia's economy if it disrupts Sunday's election in Ukraine.
Some information for this report provided by Reuters.