The Gulf states are to quit the Arab League observer mission in Syria after President Bashar Assad rejected a plan to end the country's bloodshed.
The decision by the six-nation bloc follows a move by Saudi Arabia to remove its 13 monitors.
The Gulf exit could expand rifts within Arab states about how hard to push Assad, whose forces have waged relentless attacks against opposition groups and mutinous security forces for 10 months. The UN estimates 5,400 people have died in the violence.
The group includes Saudi Arabia, Kuwait, Qatar, Bahrain, Oman and the United Arab Emirates - which comprised more than half of the 11-nation Arab monitoring mission.
Damascus has rejected an Arab League peace plan calling for a unity government within two months, which would then prepare for parliamentary and presidential elections to be held under Arab and international supervision.
The proposal also provides for Assad to give his vice president full powers to cooperate with the proposed government to enable it to carry out its duties during a transitional period.
The Arab League's observer mission has come under heavy criticism for failing to stop the violence in Syria.
The head of the mission defended the observers' work, saying their presence had cut down on the bloodshed. Speaking at League headquarters in Cairo, Sudanese Gen. Mohammed Ahmed al-Dabi said the observers have witnessed violence from both the Syrian security forces and armed opposition groups.
Syria's foreign minister responded by saying "half the universe" was conspiring against the country and that the government will take any steps to defend against chaos.
Foreign Minister Walid al-Moallem suggested that the military crackdown will continue. "It is the duty of the Syrian government to take what it sees as necessary measures to deal with those armed groups that spread chaos," he said.