US Vice President Joe Biden has spoken to Ukrainian President Viktor Yanukovich today by phone, the White House announced.
This is the latest in a series of calls between the two men since clashes between anti-government protesters and riot police erupted in the capital Kiev.
Ukraine's interim President has expressed concerns about signs of separatism as opposition in Russian-speaking regions grows.
Hundreds of Ukrainians and journalists flocked to the presidential palace, as reports emerged that President Yanukovich had left the city.
Vitali Klitschko was met with boos from anti-government protesters, as he attempted to convince them a peace deal is best course of action.