The White House is blaming increased tensions in Ukraine on its government for failing to acknowledge its people's legitimate grievances, and is threatening sanctions if the use of violence continues.

National Security Council spokeswoman Caitlin Hayden says the U.S. is deeply concerned about violence in Kiev. That's where anti-government protests escalated into fiery street battles with police Sunday in a sharp escalation of Ukraine's two-month political crisis.

Hayden says Ukraine is weakening the foundations of its democracy by criminalizing protests. She's calling on Ukraine to repeal recent laws limiting protests, remove riot police from downtown Kiev and start talking to the opposition.

The White House says the U.S. is considering sanctions among other steps if the government uses violence, echoing a warning from the State Department last month.