In a statement from the president's press secretary, the United States called on Syrian President Bashar Assad to stop killing protesters.
"The United States is deeply disturbed by credible reports that the Assad regime continues to indiscriminately kill scores of civilians and army defectors, while destroying homes and shops and arresting protesters without due process," Press Secretary Jay Carney said in a statement.
Carney also said it was time for the "suffering and killing to stop." He continued:
"We urge Syria's few remaining supporters in the international community to warn Damascus that if the Arab League initiative is once again not fully implemented, the international community will take additional steps to pressure the Assad regime to stop its crackdown."
The White House statement — which The Guardian calls its "most strident" on the situation — comes a day after rights activists said the Assad regime had undertaken "large-scale killings." Over a 48-hour period, reports CNN, 250 people have been killed, including about 100 defecting soldiers.
CNN adds that the Syrian opposition called on the United Nations to take action. The Syrian National Council said the U.N. Security Council should call an emergency meeting to "declare the cities and towns being brutally attacked 'safe zones' that enjoy international protection; and force the regime's forces to withdraw from said areas."
The U.S. has in the past ruled out a Libya-style military intervention in Syria. The BBC reports that France, which was early to call for a no-fly zone in Libya, is backing action from the Security Council.
"There was a massacre of an unprecedented scale in Syria on Tuesday," French foreign ministry spokesman Bernard Valero told the BBC. "It is urgent that the U.N. Security Council issues a firm resolution that calls for an end to the repression."