By John Irish and Louis Charbonneau
UNITED NATIONS (Reuters) - Envoys from the United States, Russia, France, China and Britain have come to an agreement on the core of a U.N. Security Council resolution to get rid of Syria's chemical weapons, three Western diplomats said on Wednesday, but Russia denied such an accord had been reached and insisted work was "still going on."
Diplomats from the five veto-wielding permanent members of the Security Council have been haggling over the details of a resolution to back an accord hammered out by Russia and the United States on September 14 in Geneva to eliminate Syrian President Bashar al-Assad's chemical weapons arsenal.
Wednesday's development came after the foreign ministers of the five council powers met over lunch with U.N. Secretary General Ban Ki-moon, the diplomats said, speaking on condition of anonymity.
Several envoys said a draft resolution could be presented to the full 15-nation council soon, and the five permanent members would also meet on Friday to discuss a proposed Syria peace conference in Geneva.
"We have a few details to solve. But I think we shall reach a common resolution maybe today or tomorrow," said French Foreign Minister Laurent Fabius.
A Western diplomatic source said: "It seems that things are moving forward," adding that there was "an agreement among the five on the core."
"We are closer on all the key points," he said. A third diplomat also suggested a deal on the draft resolution was within reach.
However, Russia rejected the Western diplomats' suggestions that there was an agreement on the core of a draft resolution.
"This is just their wishful thinking," said the spokesman for Russia's U.N. delegation. "It is not the reality. The work on the draft resolution is still going on."
A U.S. official cited progress while cautioning that there was still work to be done. "We're making progress but we're not done yet," the official told Reuters.
One of the Western diplomats said "there has been real progress. There was an agreement between the five on the core of the project."
Another diplomat also said core issues had been agreed, but there are "still some areas of outstanding disagreement" and there were no plans yet to circulate a draft resolution to the full council - a key step before putting it to the vote.
Negotiations on a draft in New York had come to a standstill while Russia and the United States struggled to reach an agreement acceptable to both. But it appears that after talks between U.S. Secretary of State John Kerry and his Russian counterpart Sergei Lavrov on Tuesday, the deadlock was broken.
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 military force.
Another point of disagreement is the role of the United Nations in the process of destroying Syria's chemical weapons and who determines what constitutes non-compliance - the Security Council or the Organization for the Prohibition of Chemical Weapons in The Hague.
The latest draft has the council determining non-compliance, a diplomat said.
Assad agreed to destroy Syria's chemical weapons in the wake of a sarin gas strike on civilians in the suburbs of Damascus last month - the world's deadliest chemical arms attack in 25 years. He accepted a U.S.-Russian agreement that Damascus' chemical arsenal should be dismantled.
Washington blamed Assad's forces for the attack, which it said killed more than 1,400 people, and President Barack Obama threatened a U.S. military strike in response.
Russia and Assad have blamed the attack on rebels battling to overthrow him in a civil war that has been raging since 2011. More than 100,000 people have died, according to the United Nations.
Russia has been Assad's most powerful backer, delivering arms and - with China - blocking three U.N. resolutions meant to pressure Assad.
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.
A Western diplomat who had seen the latest draft before the meeting with Ban said the only reference to Chapter 7 was at the end - a threat that in the event of non-compliance the council should "impose measures" under Chapter 7. To carry out that threat, a second resolution would be needed.
There is, the diplomat said, no reference to Chapter 7 in the rest of the resolution, though the language is identical to what would normally be in a Chapter 7 resolution.
INSPECTORS RETURN TO SYRIA
U.N. chemical weapons inspectors returned to Syria on Wednesday to continue investigating allegations of chemical weapons use. A convoy of five United Nations cars carrying at least eight members of the team arrived at a central Damascus hotel shortly before midday, witnesses said.
At the time of the August 21 sarin attack, the inspectors had been in Damascus preparing to investigate three earlier cases of suspected chemical weapons use, including one in March in the northern town of Khan al-Assal.
In another development, thousands of Syrian rebels have broken with the Western-backed coalition and called for a new Islamist front, undermining international efforts to build up a pro-Western military force to replace Assad.
Ever more divided on the battlefield - where Assad's better armed troops have been gaining ground - allies of the Free Syrian Army were among 13 disparate rebel factions to disown the exile leadership and build an Islamic alliance that includes the al Qaeda-linked Nusra Front, commanders said.
Details of the numbers of fighters involved how they would cooperate remained unclear. In an online video, a leader of the Islamist Tawheed Brigade said the bloc rejected the authority of the Syrian National Coalition and the Western and Saudi-backed exile administration of Ahmad Tumeh.
The move was a setback for foreign leaders trying to bolster more secular rebel groups and to reassure voters skeptical of deeper involvement in Syria's civil war. Some may think again about help for the fighters, which ranges from weaponry from the Gulf to non-lethal aid from Europe and the United States.
Seven al Qaeda-affiliated rebels were killed in a battle with a Syrian Kurdish militia on Wednesday in Atma, a town on the Turkish border which is a main escape route for fleeing refugees, as violence between Syria's Arabs and Kurds increased, opposition activists said.
The fighting showed how the region has become a battleground for a large number of armed groups in a scramble to grab territory, opposition sources said.
(Additional reporting by Erika Solomon, Stephen Kalin and Dominic Evans in Beirut, Khaled Yacoub Oweis in Amman, Dasha Afanasieva in Istanbul and Asma Alsharif at the United Nations.; Writing by Will Dunham; editing by Christopher Wilson)