By Elena Teslova

MOSCOW

President Vladimir Putin said Thursday that despite coordination between Russia and Iran on Syria, not all problems have been resolved.

The bilateral meeting came before the start of a trilateral summit between the presidents of Turkey, Russia and Iran at the Rus Sanatorium in the coastal city of Sochi.

"We are working very closely on the settlement of the Syrian problem, but not all issues have been resolved, there is a lot to talk about," Putin said.

He mentioned "scaled" Russian-Iranian nuclear energy projects.

"Large-scale projects in nuclear energy are being promoted, I hope the meeting will give impulse to the development of relations between Iran and Russia," he said.

Russian nuclear energy company Rosatom was the main contractor of Iran's Bushehr Nuclear Power Plant which opened in 1975. Now the two countries are negotiating to build more reactors.

Putin, Rouhani and Turkey's President Recep Tayyip Erdogan have gathered in Sochi to discuss a long-term solution to the crisis in Syria.

The leaders first met in Sochi in 2017.

Turkey, Russia and Iran are guarantor countries which brokered a cease-fire in Syria in December 2016, leading to the Astana talks, which are running parallel to the Geneva talks.

Syria has been locked in a vicious civil war since early 2011, when the Assad regime cracked down on protesters with unexpected ferocity.

Since then, hundreds of thousands of people are believed to have been killed and millions more displaced by the conflict.