MOSCOW (AP) — Russia on Thursday said it would not endorse a call for Syrian President Bashar Assad to give up power and criticized as inappropriate US comments that it had agreed to plans for a new national unity government in Syria that could include the opposition.

Opposition forces said they would not accept any plan that did not call for Assad’s resignation. According to a report in Al Arabiya, leaders of the opposition were prepared to decline Kofi Annan’s proposal.

Samir Nashar, a member of the Syrian National Council told Al Arabiya that “if it does not clearly state that Assad must step down, it will be unacceptable to us.”

Meanwhile, Foreign Minister Sergey Lavrov insisted that major powers meeting Saturday in Geneva for talks on Syria must concentrate on convincing opposition groups to soften their demands. He also denied a claim by a senior US official that Russia was among the backers of a plan for a new government to oversee the drafting of a new constitution and eventual elections.

“We are not supporting and will not support any external meddling,” he said. “External players must not dictate … to Syrians, but, first of all, must commit to influencing all the sides in Syria to stop the violence.”

Diplomatic hopes have rested on Russia — Syria’s most important ally, protector and supplier of arms — agreeing to a plan that would end the Assad family dynasty, which has ruled Syria for more than four decades. But the country — one of the five permanent Security Council members along with Britain, China, France and the US — has warned it would firmly oppose any document urging Assad to step down.

Moscow also has rejected efforts by outside forces to end the country’s bloody conflict or any plan to force regime change in Damascus, insisting that any plans for the future rest entirely with Syria.

It was not clear, however, whether Moscow had rejected Annan’s plan altogether or had simply not agreed to its final form.

“First of all, no agreed-upon projects exist, the work on the possible final document is going on, including a meeting of experts in Geneva,” Lavrov told reporters. “I think that the fact that certain formulas, certain ideas proposed for the possible final document by certain countries are leaked to the media manifests an improper approach to diplomacy.”

A senior US diplomat, speaking on condition of anonymity because the official was not authorized to discuss diplomatic negotiations, said international envoy Kofi Annan had assured the United States that world powers gathering in Geneva had endorsed the plan and that Russia was among its backers.

Lavrov said that diplomatic efforts should focus on urging the opposition groups to stop “their uncompromising approach and, in accordance with the Kofi Annan plan, sit down for negotiations with the government.”

Lavrov also criticized the exclusion of major regional player Iran from Saturday’s high-level meeting of the five permanent members of the UN Security Council in Geneva.

“Iran is undoubtedly a powerful player in the whole situation,” Lavrov said. “Leaving it out of the loop of the Geneva meeting is a mistake.”

The Times of Israel staff contributed to this report.