MOSCOW, May 16 (Xinhua) -- Russian Prime Minister Vladimir Putin said on Saturday that his country has become Turkey's leading trade partner. Trade turnover between Russia and Turkey reached a record 35 billion U.S. dollars, making Russia one of the most important trade and economic partners of Turkey, Putin said during talks with his Turkish counterpart Recep Tayyip Erdogan in the Black Searesort of Sochi. heads of government hailed the cooperation between the two countries. "If several years ago we talked mostly about cooperation in the construction sector, now diversification is very broad," Putin was quoted as saying by the Itar-Tass news agency. The premiers agreed to immediately start talks on extending two agreements under which Russia delivered natural gas to Turkey, the third largest consumer of Russian gas after Germany and Italy. Meanwhile, Russian companies are expected to participate in building four nuclear power plants in Turkey.