UN-Arab League envoy Kofi Annan is due to brief the UN Security Council on Friday about his peace mission to Syria where pro-democracy protests have deteriorated into bloody turmoil.

Council diplomats say Annan's assessment of the crisis will be crucial to a bid by the United States and its European allies to pass a resolution on Syria. Russia and China have already twice vetoed draft resolutions condemning Syria.

Negotiations on a draft resolution are expected to accelerate after Annan's briefing, diplomats said. It was still unclear if Russia would support a resolution on Syria, where protests against President Bashar al-Assad began a year ago.

Syria said on Wednesday it responded positively to proposals by Annan for ending the escalating violence that has killed thousands of civilians. Annan's spokesman had said questions remained over Syria's response.

The United Nations estimates Syrian security forces have killed well over 7,500 people. Syria said in December that "terrorists" had killed more than 2,000 soldiers and police.

Annan, the former United Nations secretary-general who will brief the UN Security Council via video conference, met Assad in Damascus over the weekend and outlined proposals including a halt to fighting, humanitarian access and starting a political dialogue with the Syrian opposition.

UN Secretary-General Ban Ki-moon appealed to Assad on Monday to act within the next few days on peace proposals.

In the UN Security Council, Russia, supported by China, has vigorously opposed action against Damascus by the 15-nation UN Security Council for more than six months.

The two veto powers have vowed to prevent Washington, Paris and London from pursuing Libya-style regime change in Syria, a strong ally of Moscow and home to the Russian navy's only warm-water port outside the former Soviet Union.