Will Russia discuss Syria? It appears so.

Russian Foreign Minister Sergei Lavrov will attend a meeting on the escalating conflict in Syria that international mediator Kofi Annan is attempting to organize in Geneva this weekend, Russia's U.N. Ambassador Vitaly Churkin said on Tuesday.

"Sergei Lavrov has officially accepted the invitation to come to the actual meeting in Geneva on Saturday, June 30," Churkin told reporters ahead of a closed-door meeting of the U.N. Security Council on Syria. "We attach great importance to this meeting."

U.S. officials traveling with Secretary of State Hillary Clinton, who flew to Finland on Tuesday starting a three-nation tour that will see her meet with Lavrov on Friday in St. Petersburg, said no decision had yet been made on her attendance.

"The sticking point is a clear agreement that there needs to be political transition," one senior U.S. official told reporters on board Clinton's plane, repeating U.S. opposition to Annan's proposal that Iran be included in any such talks.

"We don't think Iran has been a constructive player on this issue," the official said. "Nothing has changed in that position."

Annan's deputy, Nasser al-Kidwa, was briefing the 15-nation council by video-link on Annan's attempts to prevent the total collapse of his moribund six-point peace plan.

Diplomats said it was not entirely clear that the meeting of the five permanent Security Council members and key regional players scheduled for Saturday will take place. Annan has said that Iran should attend, but diplomats say the United States, Saudi Arabia and others dislike that idea.

Several Western diplomats said there was no agreement on what the value of the meeting would be. But Churkin made clear that Moscow expected the Saturday meeting to go ahead.

"I hope other planned participants are going to be there as well," Churkin said. "We hope it can provide powerful impetus for political efforts to put an end to the conflict."

Reference to Iran? 

So far Annan's attempts to get the opposition and government to begin a dialogue aimed at ending the 16-month conflict have failed. Annan has said that a "contact group" of the permanent council members and regional players could pressure the Syrian government and opposition to begin political negotiations.

One diplomat inside the council chamber told Reuters that Kidwa said "it's essential states with influence agree themselves on principles and guidelines to support a Syrian-led political transition."

He added that Kidwa said an "agreement on principles and scope of participation" - possibly a reference to whether Iran should take part - would be needed before the June 30 meeting could go ahead.

So far, envoys said, there is no such agreement among the five permanent Security Council members - the United States, Britain, France, Russia and China.

The U.S. official, briefing reporters with Clinton, indicated there were still hurdles to overcome, saying the meeting needed clear agreement that Syrian President Bashar al-Assad should make way for a political transition.

"If Kofi Annan can get the proposed participants to agree on such a plan for political transition then there will be a meeting. But that's what we need to find out before we go to any meeting. There's no point in going just for the sake of it," the official said.

Russia, joined by China, has thus far used its Security Council veto to block Western- and Arab-backed moves for tougher U.N. action on Damascus, which has long been a key regional Russian ally and an important market for Russian arms.

(Reporting By Michelle Nichols and Louis Charbonneau; additional reporting by Andrew Quinn in Helsinki; Editing by Vicki Allen and Xavier Briand)