MOSCOW (Reuters) -- Turkey has agreed "in principle" to allow the South Stream gas pipeline to pass through its territorial waters, a senior Russian official has said, ahead of a visit by Prime Minister Vladimir Putin to Turkey.
Putin's trip follows a signing ceremony in Ankara last month for transit agreements for the rival Nabucco gas pipeline, a European Union-backed project designed to counter Russia's strong influence on European energy supplies.
"An agreement has been reached in principle to start construction work," Yury Ushakov, deputy head of government staff, told a news briefing. He said the Turkish government will also give permission to begin a feasibility study "within days."
Ushakov said a protocol on cooperation in the gas industry, due to be signed by Putin and Turkish Prime Minister Recep Tayyip Erdogan on August 6 in Ankara, would also fix a date for the start of construction work.
Russia, which supplies a quarter of Europe's natural gas, wants to accelerate construction of gas supply routes to bypass Ukraine and other ex-Soviet states after rowing with Kyiv over transit payments several times in recent years.
Some consumers in Europe are also seeking alternative routes, such as Nabucco, that would cut dependence on Russian gas by drawing on reserves in the Caspian Sea and Central Asia.
Had Turkey rejected the South Stream project, Russia would have been forced to go through Ukraine's territorial waters.
Ushakov said the agreement does not mention any gas-marketing rights for Turkey -- a thorny issue in Turkey's previous negotiations with Russia over gas transit to Europe, as well as in talks on the Nabucco project.
Ankara is also looking for Russian oil that would fill up a planned government-backed oil pipeline that is expected to travel from the Black Sea coastal town of Samsun to the Mediterranean oil hub of Ceyhan.
Ushakov said the two sides will "express readiness to start a realization" of the project and agree to create a working group. He said Russia made some concessions on the oil-pipeline issue in exchange for Turkish concessions on South Stream.
"We made a compromise of sorts," he said.
"They made concessions on South Stream. We made some concessions on the Samsun-Ceyhan pipeline. The concessions are that we need to carefully study this project.
"Maybe it doesn't make sense to start it at all, although the Turkish side is insisting on it," Ushakov said.