* Three countries adopt joint declaration on Syria
* Moscow: Russia, Iran, Turkey wield influence on the ground
* Russia criticises U.S. efforts to resolve crisis (Recasts, adds quotes, details)
By Maria Tsvetkova and Peter Hobson
MOSCOW, Dec 20 (Reuters) - Russia, Iran and Turkey said they were ready to help broker a Syrian peace deal after the three countries held talks in Moscow on Tuesday and adopted a declaration which set out the principles any agreement should adhere to.
The countries made the announcement after Russian Foreign Minister Sergei Lavrov hosted talks with his Iranian and Turkish counterparts and Russian Defence Minister Sergei Shoigu held parallel talks with his Iranian and Turkish opposite numbers.
The document, which Shoigu called the "Moscow Declaration", said the trio were confident it would revive the moribund peace process. It also backed an expanded ceasefire.
"Iran, Russia and Turkey are ready to facilitate the drafting of an agreement, which is already being negotiated, between the Syrian government and the opposition, and to become its guarantors," the declaration said.
"They (Iran, Russia and Turkey) have invited all other countries with influence over the situation on the ground to do the same (help get a deal)," it said.
The move underlines the growing strength of Moscow's links with Tehran and Ankara, despite the murder on Monday of Russia's envoy to Turkey, and reflects Putin's desire to cement his country's growing influence in the Middle East and more widely.
It also shows how fed up Russia is with what it sees as long and pointless talks with the Obama administration over Syria. Russian Foreign Minister Sergei Lavrov last week dismissed those talks as "fruitless sitting around."
'REAL INFLUENCE ON GROUND'
President Vladimir Putin said last week that he and his Turkish counterpart Tayyip Erdogan were working to organise a new series of Syrian peace negotiations without the involvement of the United States or the United Nations.
He said those talks could take place in Astana, the capital of Kazakhstan, a close Russian ally.
Russia says that the talks, if they happen, would be in addition to intermittent U.N.-brokered negotiations in Geneva.
Lavrov said on Tuesday he thought what he called the Russia-Iran-Turkey troika was the most effective forum when it came to trying to solve the Syria crisis.
Shoigu said only Russia, which has backed President Bashar al-Assad with air strikes, special forces and military advisers, and Iran and Turkey were able to make a real difference.
"All previous attempts by the United States and its partners to agree on coordinated actions were doomed to failure," Shoigu said. "None of them wielded real influence over the situation on the ground."
Russia and Iran both back Assad, but Turkey, a NATO member, has long made clear it would prefer him to step down. Ankara has however moderated its rhetoric on Assad in recent months, and Lavrov said all three countries agreed the priority was to fight terrorism rather than to remove the Syrian leader.
The declaration said any Syria settlement should respect the country's territorial integrity.
"The ministers agreed the importance of expanding the ceasefire, unhindered access for humanitarian aid and free movement of civilians across Syria," it said. (Editing by Andrew Osborn)
Our Standards: The Thomson Reuters Trust Principles.