US Secretary of State John Kerry arrived in Moscow December 15 to try and narrow differences with Russian leader Vladimir Putin over the role of Syrian President Bashar al-Assad in any political transition and which rebel groups should be part of peace talks.
Kerry will seek to prepare the ground for a third round of talks of world powers on Syria amid doubts over whether a meeting pencilled in for December 18 in New York will go ahead.
Russia's Foreign Ministry said late on December 13 that Kerry and Russian Foreign Minister Sergei Lavrov agreed in a phone call on the need for specific preconditions to be met before any new meeting, throwing the timing into doubt.
However, US State Department spokesman Mark Toner said there were no preconditions to having this meeting.
Russia is one of Assad's staunchest allies and launched a campaign of air strikes to support his forces against insurgents on Sept. 30. It says only the Syrian people and not external powers should decide Assad's political fate.
Speaking before Kerry's arrival in Moscow, a State Department official said Kerry would also raise concerns about Russia's continued bombing of Syrian opposition forces instead of Islamic State militants, an approach likely to anger Moscow.
Ahead of the talks, 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 meeting with Putin follows a meeting last week in Riyadh which agreed to unite a number of opposition groups excluding Islamic State to negotiate with Damascus in Syrian peace talks.
While Kerry said there were still "kinks" that needed to be worked out, mainly to do with which groups should be included in peace talks, the Kremlin rejected the outcome of the Riyadh meeting, saying some of the groups were considered terrorists.
Assad himself appeared to cast doubt on the very idea of peace talks on December 18, saying he would not negotiate with armed groups that he said were backed by the United States and Saudi Arabia.
The opposition groups said Assad should leave power at the start of a transitional period.
