US Secretary of State John Kerry is in Moscow for talks to try to bridge gaps with Russia over the political process to end Syria’s civil war.
He is now in talks with Foreign Minister Sergei Lavrov and will later meet President Vladimir Putin.
The US and Russia have long disagreed on what role Syrian President Bashar al-Assad should play in the process.
The US wants Mr Assad to stand down but Russia says only the Syrian people can decide his fate.
Ahead of the talks, the Russian foreign ministry attacked US policy, accusing Washington of “dividing terrorists into good and bad ones”.
Russia has been carrying out air strikes it says target position of the Islamic State (IS) group in Syria, but the US accuses Russia of bombing moderate rebels to shore up its ally President Assad. Moscow denies the allegations.
A US-led coalition has been targeting IS militants in Syria since September 2014 and does not co-ordinate its raids with the authorities in Damascus.
Russia has also rejected the outcome of a meeting of Syrian opposition groups, who agreed to unite to hold peace talks but stressed President Assad could not participate in a political transition.
As the meeting with Mr Lavrov began, Mr Kerry said: “The world benefits when powerful nations can find common ground and I hope today we can find some common ground.”
On Islamic State, he said Russia and the US both agreed it was “a threat to every country… these are the worst of terrorists, they leave no choice but for civilised nations to join together and push them back and destroy them”.
Mr Kerry will try to prepare the ground for an international meeting on Syria mooted for later this week.
There are some doubts whether it will go ahead but the US state department denied claims from Russia “preconditions” would have to be met for the meeting to take place.
Negotiations between the Syrian government and the opposition have been tentatively scheduled for January next year.
Mr Lavrov said the IS issue was not limited to Syria, as the group was also active in Iraq, Afghanistan and Yemen.
He also said the meeting would cover the matter of Ukraine, with its continued division between the Western-backed government in Kiev and the Russian-backed separatists in its east.
Mr Kerry said: “Nothing would please us more than to solve the problem of Ukraine and move forward on the economic front.”
Why is there a war in Syria?
Anti-government protests developed into a civil war that, four years on, has ground to a stalemate, with the Assad government, Islamic State, an array of Syrian rebels and Kurdish fighters all holding territory.
Who is fighting whom?
Government forces concentrated in Damascus and the centre and west of Syria are fighting the jihadists of Islamic State and al-Nusra Front, as well as less numerous so-called “moderate” rebel groups, who are strongest in the north and east. These groups are also battling each other.
What’s the human cost?
More than 250,000 Syrians have been killed and a million injured. Some 11 million others have been forced from their homes, of whom four million have fled abroad – including growing numbers who are making the dangerous journey to Europe.
How has the world reacted?
Iran, Russia and Lebanon’s Hezbollah movement are propping up the Alawite-led Assad government, while Turkey, Saudi Arabia and Qatar back the more moderate Sunni-dominated opposition, along with the US, UK and France. Hezbollah and Iran are believed to have troops and officers on the ground, while a Western-led coalition and Russia are carrying out air strikes.