Wary of the cease-fire, Britain and France took the lead in plans to enforce a no-fly zone, sending British warplanes to the Mediterranean and announcing a crisis summit in Paris with the U.N. and Arab allies. In Washington, President Barack Obama ruled out the use of American ground troops but warned that the U.S., which has an array of naval and air forces in the region, would join in military action.

There should be no doubt about the Libyan leader's intentions "because he has made them clear," Obama said. "Just yesterday, speaking of the city of Benghazi, a city of roughly 700,000, he threatened `we will have no mercy and no pity.' No mercy on his own citizens."