The Syrian opposition cast doubt on whether it would go to peace talks planned for Friday, throwing U.N. diplomatic efforts into question and accusing the United States of adopting Iranian and Russian ideas for solving the conflict.

The Saudi-backed opposition was meeting on Tuesday to decide whether to attend the talks which U.N. envoy Staffan de Mistura aims to open in Geneva on Friday, ushering in months of negotiations with delegates in separate rooms.

Opposition official Asaad al-Zoubi told Arabic news channel Al-Hadath that he was pessimistic, though the final decision would be taken at the opposition meeting in Riyadh.

De Mistura was expected to issue invitations on Tuesday.

"It's going to be very low-key proximity talks," U.N. spokesman Ahmad Fawzi told journalists in Geneva.

A Western diplomat said the aim was to get the talks started without further delay. "There is a little bit of fear that if the talks don't start soon they'll never really get going."

The Syrian government, which is taking territory from the rebels with the help of Russian air strikes and Iranian ground forces, has already said it will attend.

The opposition comprising the recently formed High Negotiations Committee (HNC) has however repeatedly said the government and its allies must halt bombardments and lift blockades of besieged areas before they will go to any talks.

Zoubi, who is due to head the opposition delegation to any negotiations, told Reuters that without the implementation of goodwill steps including release of detainees "there will be no negotiations". "This is what the HNC has laid down," he said.

Reflecting opposition misgivings about the process, he told Al-Hadath that U.S. Secretary of State John Kerry had tabled Iranian and Russian ideas about Syria at a recent meeting with opposition leader Riad Hijab.

"It was not comfortable for us for America - even in theory or partially - to adopt what came in the Iranian and Russian initiatives," Zoubi said in the interview.

He also heaped criticism on de Mistura, saying the U.N. Syria envoy "cannot impose conditions" on the opposition.

The U.S. Special Envoy for Syria, Michael Ratney, urged the opposition to attend the talks.

"Our advice to the Syrian opposition is to take advantage of this opportunity to put the intentions of the regime to the test and to expose in front of international public opinion which are the parties serious in reaching a political settlement in Syria and which are not," he said.

LOST LEGITIMACY

The United States has supported the opposition to President Bashar al-Assad, who it says has lost legitimacy and must leave power. But the opposition has been increasingly critical of U.S. policy. Hijab said earlier this month the United States had backtracked on its position over Syria, softening its stance to accommodate Russia.

Preparations for the talks have been beset by problems including a dispute over who should represent the opposition.

Russia has sought to expand the opposition delegation to include a powerful Kurdish faction that controls wide areas of northern Syria. The Sunni Arab opposition say the Kurdish PYD party should be part of the government delegation.

De Mistura has said the Geneva meeting will aim to kick off six months of talks, first seeking a ceasefire, later working toward a political settlement to a war that has killed more than 250,000 people and forced than 10 million to flee.

Russian Foreign Minister Sergei Lavrov said on Tuesday it would be impossible to reach a peace agreement in Syria without inviting Kurds to take part in the negotiating process.

It would be "unfair" and "counter-productive" to stop Syrian Kurds from taking part in the peace talks, Lavrov said. He also said some participants of the peace process had been "capricious" in refusing to negotiate.

Turkey, a major sponsor of the insurgency, however said it was against the participation of the Kurdish YPG militia which is affiliated to the PYD. The YPG has become an important partner in the U.S.-led fight against Islamic State.

Turkey views the YPG as an extension of the PKK, which it sees as a terrorist organization. "Those who are recognizing them as a legitimate partner, they don't live in the reality of the region, nobody can convince us that these people are for peace,� Turkish Prime Minister Ahmet Davutoglu told CNN.

The Syrian government and its allies have made significant gains against rebels in western Syria in recent weeks.

On Monday they captured the rebel-held town of Sheikh Maskin in southern Syria near the border with Jordan. It was the first significant gain for Damascus in that area since the start of the Russian intervention on Sept. 30.

In recent weeks government forces and their allies have also captured two strategic towns in the northwestern province of Latakia, where they are trying to seal the border to cut insurgent supply lines to Turkey.

By Reuters