UNITED NATIONS, Sept 24 (Reuters) - U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov worked in a "constructive spirit" on Tuesday on a draft U.N. Security Council resolution on Syria's chemical arms but more work is needed by U.N. envoys, a U.S. official said.
Kerry and Lavrov met for about 90 minutes on the sidelines of the annual gathering of world leaders at the United Nations.
The five veto-wielding permanent members of the Security Council - Russia, the United States, France, Britain and China - have been negotiating a resolution to demand the destruction of Syria's chemical arsenal in line with a U.S.-Russian deal.
"The constructive spirit in which the two ministers engaged should help us in our work going forward," said a senior U.S. State Department official, speaking on condition of anonymity.
"There were three or four key conceptual hurdles that had to be bridged. The ministers did the conceptual work, I would say, and now that has to be turned into text," the official added.
The official said U.S. Ambassador to the United Nations Samantha Power and Russian U.N. Ambassador Vitaly Churkin would now need to do more work on the draft text to reach agreement.
A major sticking point between Russia and Western powers has been whether the resolution is written under Chapter 7 of the U.N. charter, which covers the Security Council's authority to enforce decisions with measures such as sanctions or force.
Russia has made clear it would not accept an initial resolution under Chapter 7 and that any punitive measures would come only in the event of clearly proven Syrian non-compliance on the basis of a second council resolution under Chapter 7.
U.S. officials did not explain how or whether the resolution under discussion might make reference to Chapter 7.
"We need a resolution that is clearly binding ... enforcible, verifiable," said the U.S. official, without elaborating on how this might be achieved.
Earlier this month Russia and the United States agreed to a deal in Geneva that calls for Syria to account fully for its chemical weapons and for the removal and destruction of the entire arsenal by mid-2014.
Syria acceded to the Chemical Weapons Convention in line with the U.S.-Russian deal.
That deal was agreed after President Barack Obama threatened to launch U.S. air strikes against Syria because of an Aug. 21 poison gas attack, which Washington blames on Syrian government forces. Syria and Russia say the sarin attack, which killed hundreds, was carried out by Syrian rebels.
U.N. chemical weapons investigators led by Ake Sellstrom of Sweden have confirmed the use of sarin nerve agent in the attack.
The 15-member U.N. Security Council has been deadlocked on how to deal with the 2-1/2-year-old Syrian civil war.
Syrian ally Russia, backed by China, has vetoed three council resolutions since October 2011 that would have condemned Syrian President Bashar al-Assad's government and threatened it with sanctions.