By Stephanie Nebehay and Tom Miles
GENEVA (Reuters) - The United States and Russia failed on Tuesday to agree on a date for a Syrian peace conference, remaining divided over what role Iran might play in talks to end the civil war and over who would represent Syria's opposition.
"We were hoping that we would be in a position to announce a date today; unfortunately we are not," said U.N.-Arab League envoy Lakhdar Brahimi, who chaired the meeting at the United Nations in Geneva. "But we are still striving to see if we can have the conference before the end of the year."
Brahimi conferred with senior U.S. and Russian officials before widening the talks to include representatives from Britain, France and China, as well as Syria's neighbors Iraq, Jordan, Lebanon and Turkey, and the Arab League.
Brahimi said he would bring Russian and U.S. officials together again on November 25 and hoped that opponents of Syrian President Bashar al-Assad would have agreed on delegates to represent them some days before that.
"The opposition has a very, very difficult time," he said. "They are divided. It is no secret for anybody. They are facing all types of problems and they are not ready."
Russian Deputy Foreign Minister Gennady Gatilov, who met Brahimi along with fellow Deputy Foreign Minister Mikhail Bogdanov, said the United States, which has backed the revolt against Assad, did not have the leverage needed to assemble a credible opposition delegation representing various factions.
"It is not just the representation of the opposition that is required, but the participation of an opposition delegation of a broad range of opposition forces. And this is what the Americans are failing to achieve," RIA news agency quoted him as saying.
Washington was represented at the talks with Brahimi by State Department Under Secretary Wendy Sherman and Robert Ford, the U.S. ambassador to Syria.
A senior U.S. official said they had been "very substantive and very helpful", adding: "We are very hopeful that this conference will take place before the end of the year."
"If it takes the opposition coalition a few more weeks to prepare themselves in the way they feel they need to, to be full partners, a full delegation at a conference, then we want to support them to do that," the official said.
The proposed peace conference is meant to build on a June 2012 agreement among world powers in Geneva that called for a transitional authority with full executive powers, but did not explicitly say Assad should step down.
Damascus reiterated on Monday that Assad would stay in power come what may, casting doubt on the political transition that is the main focus of the proposed "Geneva 2" conference.
"Syria - the state, the nation and the people - will remain and ... Assad will be president of this country all the time they are dreaming that he isn't," the Syrian state news agency quoted Information Minister Omran Zoabi as saying on Monday.
International efforts to end the conflict in Syria, which has killed well over 100,000 people, driven millions from their homes and further destabilized the region, have foundered.
"One thing is certain - there is no military solution for the conflict in Syria," U.S. Secretary of State John Kerry said in Warsaw on Tuesday, asserting again that Assad must go. "I don't know how anybody believes the opposition is going to give mutual consent to Assad to continue."
Russia said Iran, Assad's main sponsor, must be invited to any peace talks, after the main Syrian political opposition leader said his coalition would not attend if Tehran took part.
The U.S. official said Washington recognized Iran was going to play a role in the region and wanted to ensure it was not a negative one. "But ... the United States believes everybody who comes to the Geneva conference should subscribe to the Geneva communique, have made that commitment before they come. Iran has not chosen to do that."
The official also pointed to the Lebanese shi'ite group Hezbollah, which is backed by Iran and is fighting alongside Assad's forces in Syria. "Obviously we have some great concerns about Iran's participation in the conflict and Iran's financing of Lebanese Hezbollah," the official said.
Russian Foreign Minister Sergei Lavrov also rejected a demand by Syrian National Coalition chief Ahmad Jarba for a time-frame for Assad to quit, ruling out any such preconditions for "Geneva 2".
Moscow has defended Assad from Western and Arab efforts to impose U.N. sanctions. Having been a major arms supplier to the Syrian government, Moscow notes that attempts to end the four-decade rule of the Assad family have turned parts of Syria over to rebel groups controlled by Islamist militants.
The civil war has inflamed a sectarian divide in the Middle East. Sunni Muslims form the majority in Syria and provide the bulk of the rebel forces. They have backing from Sunni-ruled Gulf Arab states, while Shi'ite, non-Arab Iran backs Assad.
"All those with influence on the situation must certainly be invited," Lavrov told a news conference in Moscow. "This includes not only Arab countries but also Iran."
Saudi Arabia and the United States oppose any invitation for Iran.
Iranian Foreign Minister Mohammad Javad Zarif said Tehran could contribute to a peaceful solution and was willing to call for the withdrawal of all foreign forces from Syria:
"We believe that everybody should assist the Syrian parties to come to the negotiating table to seek a solution," he told France 24 television. "Those who are supporting armed groups need to do their part to end this illusion that there can be a military solution to Syria."
The Arab League gave its blessing on Sunday to the proposed peace talks and urged the opposition to form a delegation under the leadership of Jarba's coalition.
But it is unclear whether the opposition, which has scant influence with rebels fighting in Syria, will attend.
"The Qataris have been trying to hammer out a united position between the opposition, but I don't think they will succeed," said an Arab diplomat in Geneva.
"The Saudi position is complicating things. They are not too excited about Geneva 2."
Riyadh is angry over what it sees as a weak U.S. commitment to removing Assad, especially since President Barack Obama dropped a threat of air strikes after a poison gas attack near Damascus in August.
Saudi Foreign Minister Prince Saud al-Faisal criticized Iran on Monday, saying it was helping Assad attack his own people.
In response, Zoabi, the Syrian information minister, said: "We promise that Saudi diplomacy will fail, whether Geneva goes ahead or not. We will not go to Geneva in order to hand over power, as al-Faisal and some of the opposition abroad hope."
"If that was the case we would have handed it over in Damascus and saved the effort and price of the airline ticket."
(Additional reporting by Dominic Evans in Beirut, Steve Gutterman and Alexei Anishchuk in Moscow, John Irish in Paris and Lesley Wroughton in Warsaw; Writing by Alistair Lyon and Tom Miles; Editing by Alastair Macdonald and David Stamp)