By Lesley Wroughton
WASHINGTON, Feb 19 (Reuters) - The United States on Wednesday imposed visa bans on 20 senior Ukrainian government officials believed to be responsible for a violent crackdown by riot police against protesters, a senior State Department official said.
The senior official, speaking to reporters on condition of anonymity, would not name those affected by the U.S. visa ban, which bars the individuals from applying for visas to travel to the United States.
"Today we moved to restrict visas to some 20 senior members of the Ukrainian government and other individuals we consider responsible for ordering human rights abuses related to political oppression in Ukraine," the official said.
"These individuals represent the full chain of command we consider responsible for ordering the security forces to move against" the protesters, the official said, adding that the visa bans were easily reversible if the situation improved.
In December, the U.S. Embassy in Kiev said it had revoked the visas of several Ukrainians linked to police violence against demonstrators at the end of last year.
The official said a truce agreed between Ukrainian President Viktor Yanukovich and opposition leaders late on Wednesday represented "a glimmer of hope." Whether or not the truce holds would depend on talks scheduled between the government and opposition on Thursday, according to the official.
"We will watch whether this truce holds and whether they are able to move on to political compromise and a transition government that can take Ukraine forward," the official said.
"In the event that things go well these visa sanctions we put in place are reversible but in the event they do not go well there are other steps we can take in close coordination with the EU in coming days," the official added.
The European Union has said it is preparing targeted sanctions against those responsible for the violence. It has also dispatched foreign ministers from Germany, France and Poland to Kiev on Thursday, hours before an emergency EU meeting in Brussels to decide on sanctions.
U.S. officials have warned that Washington is prepared to slap financial sanctions on government officials if the bloodshed worsens.
U.S. President Barack Obama on Wednesday called on Ukraine's armed forces to stay out of the country's political crisis and warned there would be consequences for those who "step over the line."
The U.S. warning followed concerns that the military was preparing to move against protesters and after Yanukovich appointed a new head of the armed forces general staff.
The senior State Department official said there was also growing concern from Washington after U.S. officials were unable to reach senior Ukrainian military and intelligence officers by phone.
The official said the calls were meant to "express our view with regard to allowing peaceful protests and allowing political compromise."
"We have been trying to reestablish those contacts over the last few days and nobody is picking up the phone on the Ukrainian side, which is worrying," the official said, adding that the "changing of the guard" in the military was a concern and hoped it did not mean the military was ready to get involved in the anti-government protests.
While Ukraine is not presently seeking membership in NATO, it does cooperate with the Western military alliance in a number of areas.