President Obama hosted Ukrainian Prime Minister Arseniy Yatsenyuk at the White House on Wednesday in a show of support for the interim Ukraine government in its standoff with Russia. The meeting comes days before the Russian-backed government in Crimea is holding a referendum on whether to secede and join Russia. Obama warned Russia of consequences if Ukraine is divided.

President Obama: “We will continue to say to the Russian government that if it continues on the path that it is on, then not only us, but the international community, the European Union and others will be forced to apply a cost to Russia’s violations of international law and its encroachments on Ukraine. There’s another path available, and we hope that President Putin is willing to seize that path. But if he does not, I am very confident that the international community will stand strongly behind the Ukrainian government in preserving its unity and its territorial integrity.”

Borrowing the famous line from Ronald Reagan at the Berlin Wall, Yatsenyuk called on Putin to drop his designs on Crimea.

Ukrainian Prime Minister Arseniy Yatsenyuk: “So my message to President Putin: Mr. Putin, tear down this wall, the wall of war, intimidation and military aggression. Let’s stop. Let’s calm down.”

At their meeting, Obama backed a tentative proposal that would potentially open more autonomy to Crimea if Russian forces withdraw. Secretary of State John Kerry is due to hold talks with Russian counterpart Sergey Lavrov in London on Friday.