SOCHI, October 24./TASS/. The presidents of Russia and Turkey, Vladimir Putin and Recep Tayyip Erdogan, negotiated one-on-one for more than two hours during their six-hour-long talks on Syria on Tuesday, Kremlin Aide Yuri Ushakov said on Thursday.

"They spoke tete-a-tete for at least two hours," he told reporters in reply to their query. Then, work continued with the participation of the delegations, Ushakov said.

When asked about the share of Russian and Turkish initiatives in the agreement achieved on Tuesday, Ushakov said "it is difficult to say this". "This is a joint document,’" he stressed, with both Russia and Turkey making contribution.

Journalists were interested to know how difficult it had been to agree, to which the Kremlin aide noted that it had taken the presidents six hours. "Usually, such working meetings continue no longer than two to three hours, while in this case - it was six hours. The matters are very important, and a crucial document was coordinated," he added.

Russian military police started patrolling the Syrian side of the border with Turkey on Wednesday. That will help to ensure the withdrawal of the Kurdish Self-Defense Forces from the area within 150 hours. Moscow thus drew a line for Ankara’s military campaign in Syria, which began on October 9 and was suspended last week after the US-brokered ceasefire. A historic memorandum to this effect was unveiled on Tuesday after more than six hours of talks between Russian President Vladimir Putin and his Turkish counterpart Recep Tayyip Erdogan.