Western and Arab diplomats have launched a major offensive at the UN in the hope of overcoming Russia's opposition to a draft resolution demanding that Syrian President Bashar Assad relinquish power.
US Secretary of State Hillary Rodham Clinton and the British and French foreign ministers were travelling to New York for the Security Council session on the situation in Syria.
Nabil Elaraby, the chief of the Arab League, and Sheikh Hamad Bin Jassem Bin Jabr Al Thani, Qatar's prime minister, also were to brief council members.
It was unclear if the high-level push would succeed.
Russia, a veto-wielding permanent member of the council, has objected to the draft, which is backed by Western and some Arab powers. Russia's Deputy Foreign Minister Gennady Gatilov said on Twitter that the resolution is a "path to civil war."
Russia says it worries that the new measure could lead to military action and regime change, just as an Arab-backed UN resolution led to Nato airstrikes in Libya that allowed rebels to oust the regime of Muammar Gaddafi.
Backers of the draft point out that it says specifically that "nothing ... compels states to resort to the use of force or the threat of force."
An actual vote on the draft resolution was considered unlikely until later this week.
The debate came amid rising violence in Homs, a Syrian centre of opposition to Assad's regime. The UN estimates that more than 5,400 people have been killed since last March in the Syrian government crackdown against protesters.
The draft resolution demands that Assad halt the crackdown and implement an Arab League peace plan calling for him to hand over power to his vice president. If Assad fails to comply within 15 days, the council would consider "further measures," a reference to a possible move to impose economic or other sanctions.