Russia and the United States can work together to make progress in ending the war in Syria, U.S. Secretary of State John Kerry told Vladimir Putin on Tuesday, seeking to narrow their differences over a political transition in Damascus.

"We're at a strong beginning opening up possibilities," Kerry told the Russian leader at the start of their meeting. "Together the United States and Russia have an ability to make a significant difference."

Kerry is hoping his discussions with Putin and Foreign Minister Sergei Lavrov will prepare the ground for a third round of talks of world powers on Syria, penciled in for Friday in New York.

It is unclear whether the meeting will go ahead without progress between Russia and the United States over the role of Syrian President Bashar Assad in any political transition and over which rebel groups should be part of peace talks.

"We are seeking with you solutions to the most acute crisis (in Syria)," Putin told Kerry, before the two men began closed-door talks.

Earlier, Kerry had said he was looking forward to making "real progress".

"I think the world benefits when powerful nations with a long history with each other have the ability to be able to find common ground." Kerry said at the start of a meeting with Lavrov, the foreign minister.

"Even when there have been differences between us we have been able to work effectively on specific issues."

Russia, one of Assad's staunchest allies, has launched a campaign of air strikes that it said were aimed at Islamic State militants but which also supported Assad's forces. The Kremlin says the Syrian people, and not external powers, should decide Assad's political fate.

Lavrov told Kerry there was a need for more effective international cooperation in fighting terror. "On that route there are still questions which today we need to look at," Lavrov said in his opening remarks.

Important meeting

Kerry described the talks with Lavrov as "good" as he took a break to stroll in a shopping area near the residence of the U.S. ambassador to Moscow where he was mobbed by a crowd of people who wanted a glimpse of him.

Asked whether the New York meeting would happen, Kerry said: "I need to meet with the president (Putin). I look forward to that. It will be an important meeting."

The run-up to the Moscow talks underlined the distance between Moscow and Washington on how to deal with the Syria crisis.

For its part, the Russian Foreign Ministry issued a statement complaining that Washington was not ready to fully cooperate in the struggle against Islamic State militants and needed to rethink its policy of "dividing terrorists into good and bad ones".

Kerry's visit follows a meeting last week in Saudi Arabia which agreed to unite a number of opposition groups, not including Islamic State, to negotiate with Damascus in peace talks.

U.S. officials expect the talks with Putin to be dominated by the list of opposition groups that would join the talks.

A 34-member secretariat established at the Riyadh meeting is expected to meet later this week to decide matters including who will chair it. The secretariat, which includes armed factions and members of the political opposition, will also pick a negotiating team for talks with the government, though it is not certain that will happen this week.

Assad last week rejected the idea of talks with armed groups, appearing to further diminish the chances of negotiations beginning in line with a Jan. 1 target date. "It seems ambitious," said a senior Western diplomat.

The diplomat said the names suggested to head the secretariat were Riad Hijab, who briefly served as Syrian prime minister before defecting to the opposition in 2012, and Ahmad Jarba, a former head of the Syrian National Coalition opposition body.

Two sources familiar with the views of members of the secretariat said Hijab was the preferred candidate.

Tuesday's talks with Putin may also touch on the creation of a new Saudi-led Islamic alliance to fight terrorism which will share information and train, equip and provide forces if necessary for the fight against Islamic State.

Kremlin spokesman Dmitry Peskov said the new alliance was good in principle but that the devil was in the details.

"We need to understand who precisely has joined this coalition, and what aims they are declaring," he said.