US Vice President Joe Biden has warned Ukrainian President Viktor Yanukovych that America is ready to impose sanctions on officials guilty of ordering troops to fire on protesters.
Biden spoke to the Ukrainian leader by telephone and "made clear that the United States is prepared to sanction those officials responsible for the violence", the White House said in a statement on Thursday.
The call came on a torrid day in Kiev in which more than 60 people were killed in the worst carnage since the start of anti-government protests.
Washington earlier said it was outraged that government troops had turned automatic weapons on protesters and made clear that it was moving closer to imposing sanctions - a step the European Union has already taken.
The White House statement said Biden called upon Yanukovych to "immediately pull back all security forces" - police, snipers, military and paramilitary units, and irregular forces.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"The Vice President urged President Yanukovych to take immediate and tangible steps to work with the opposition on a path forward that addresses the legitimate aspirations of the Ukrainian people."
Earlier, President Barack Obama had called German Chancellor Angela Merkel to discuss the next Western response in the crisis, a day after warning of "consequences" for the government if violence continues.
Obama has already put 20 Ukrainian officials on a visa blacklist and threatened further sanctions, which could include asset freezes.
