Congressional aides, who asked not to be identified by name because of the sensitive subject, said they had discussed the sanction preparations with administration officials.

They said final details of the package have not been worked out, but it could be put in place quickly against government officials - or leaders of the protest movement - in case of widespread violence.

Six people have been killed in Kiev and other Ukrainian cities in protests that erupted more than two months ago after President Viktor Yanukovich walked away from a treaty with the European Union under pressure from Russia.

Alarmed by the crisis, Washington has revoked the visas of some Ukrainian officials.

The House Foreign Affairs Committee on Wednesday passed a resolution calling on all sides in the confrontation to refrain from violence.

However, U.S. lawmakers and Obama administration officials said they were encouraged by recent developments, including the Ukrainian parliament's vote to repeal anti-protest laws.

Alarm has grown elsewhere in the West. German Chancellor Angela Merkel telephoned Russian President Vladimir Putin and Yanukovich on Wednesday, urging a constructive dialogue between the government and opposition.

Putin raised the pressure on Ukraine on Wednesday, saying Russia would wait until Ukraine forms a new government before fully implementing a $15 billion bailout deal that Kiev urgently needs.

NJF/NJF