The United States may impose sanctions against Ukraine if security forces intensify a crackdown on anti-government demonstrators in the capital's Independence Square.
US lawmakers said on Wednesday they were considering legislation to deny visas to Ukrainian officials or to freeze their American assets if violence escalates at the central protest camp.
White House deputy spokesman Josh Earnest said the US was "appalled" at how the government has handled the political crisis.
"The Ukrainian government's response to peaceful protests over the last two weeks has been completely unacceptable... The right to peaceful protest and assembly must be respected," Earnest said.
Kiev has been gripped by weeks of demonstrations by hundreds of thousands of people against President Viktor Yanukovich's decision to reject a European Union trade pact and steer Ukraine closer to Russia.
If he continues to use bulldozers and batons to break up peaceful demonstrations, there could be consequences.
Several dozen people were injured in the early hours of Wednesday when riot police and Interior Ministry special forces moved against the demonstrators' last stronghold in Independence Square.
Security forces initially tore down makeshift barricades but were eventually forced to retreat amid cheers from the demonstrators, whose ranks swelled through the night.
US Senate and House of Representatives aides cited discussions at the staff level about Congress responding to the unrest in Ukraine with legislation along the lines of the Magnitsky Act, which bars Russian officials believed to be involved in human-rights abuses from entering the United States.
Democratic Senator Chris Murphy, who chairs the Senate's Europe subcommittee, said lawmakers would be closely monitoring Yanukovich's conduct in the days ahead.
"If he continues to use bulldozers and batons to break up peaceful demonstrations, there could be consequences, real consequences, from the Congress," Murphy said.
The US State Department said it was considering all options, including sanctions.
Ukraine's police have been criticised by the West for heavy-handedness in dealing with protests even before the latest crackdown, with dozens of demonstrators injured in clashes last week.
Yanukovich has pledged that the authorities would never use force against peaceful protests, and urged the opposition to sit down for talks.
"For the sake of achieving compromise I am calling on the opposition not to reject [talks], not to follow the path of confrontation and ultimatums," Yanukovich said in a statement on Wednesday.
But the opposition, which earlier ruled out any negotiations until he dismissed the government and punished riot police for crushing a smaller protest on November 30, pledged to do everything to topple the president.
"With what happened last night, Yanukovich closed off the path to any kind of compromise," opposition leader Vitaly Klitschko told a news conference, adding they "had planned to have talks with Yanukovich. We understand that Yanukovich has no wish to talk to the people and only understands physical force, which he uses against the protesters."
An estimated 5,000 pro-EU demonstrators were camping out in Independence Square on Wednesday night, reinforcing barricades with snow and sand bags.