As a midnight on December 4 (5 p.m. ET) deadline passed, there was no immediate indication that Syrian officials had responded to the ultimatum. Syria's state-run news agency said the country could withstand sanctions already imposed by the Arab League and by neighboring Turkey, and human rights and opposition groups said at least 22 more people were killed as the clampdown continued.

Over the weekend, Arab League officials meeting in the Qatari capital Doha responded to requests by Damascus for some clarifications to the plan, but did not make any key changes, according to Qatar's foreign minister, Hamad bin Jassim al-Thani.

Ministers agreed over the weekend to freeze the assets of more top Syrian officials, reduce flights in and out of the country by half and impose a complete ban on weapons shipments to Syria, a statement from the Arab League said.

The United Nations estimates that more than 4,000 people have died since mid-March, and the death toll continues to rise. The Local Coordinating Committees of Syria, an opposition umbrella group, said 22 people had been killed on December 4.