The prime ministers of Turkey and Russia have signed a series of agreements regarding co-operation on major oil and gas projects.
One deal is for the construction of a pipeline through Turkish waters in the Black Sea.
Moscow hopes the South Stream pipeline will become a viable new route to supply Russian natural gas to Europe.
Vladimir Putin sealed the agreement with Recep Tayyip Erdogan during a one-day visit to Ankara.
Among the other accords signed at the meeting was an agreement on peaceful nuclear co-operation, which included a push towards building Turkey's first nuclear power station.
The Russian prime minister said the negotiations would "open the road to new major projects in the energy sector".
"Such strategic projects as South Stream... and the construction of Turkey's first nuclear power plant can play a key role in promoting co-operation in this sphere," he was quoted as saying by Russia's Itar-Tass news agency.
"It is very important for the reliable supply of gas to the whole of Europe and for the further development of our co-operation with Turkey."
The South Stream pipeline, which will run from Russia to Bulgaria, will give Moscow another supply route for its gas exports to Europe. At least twice in recent years these have been disrupted by disputes with Ukraine.
Turkey is expected to benefit from Russian help with building gas storage facilities, and the increased influence that comes with being an energy hub.