US President Barack Obama gave a big show of public support to Ukraine Prime Minster Arseniy Yatsenyuk, welcoming him to the White House and warning Russian President Vladimir Putin that the international community “will be forced to apply costs” if Russia does not remove its troops from Crimea.

“We will stand with Ukraine.”

Obama said the United States and Ukraine recognized the historic ties between Russia and Ukraine, but that Ukraine's government “cannot have a country outside of Ukraine dictate to them how they should arrange their affairs.”  The US and the rest of the G7 are warning Russia not to annex Ukraine’s Crimean Peninsula, which it is currently occupying.  The two are proposing a plan that could give Russians a greater voice in the region.

 “It is absolutely unacceptable to have Russian boots on the Ukrainian ground in the 21st century, violating all international deals and treaties,” Yatsenyuk said after the meeting with Mr. Obama.

Ukraine Defense Secretary Andriy Parubiy told reporters in Kiev that Russia has moved massive forces to their common border – including more than 80,000 troops, up to 270 tanks, and 140 combat planes close to the border – creating the “threat of a full-scale invasion from various directions.”  Some are just an hour’s drive from the Ukrainian capital.

In Moscow, Deputy Defense Minister Anatoly Antonov denied a military buildup on the nearly 2,000-kilometer border.  But the US confirmed it is sending a dozen F-16s to Poland to bolster its defenses.