The two leaders are marking the completion of the offshore part of TurkStream’s two lines Turkey relies on imports for its energy needs and Russia is its top supplier for natural gas ISTANBUL: Russian President Vladimir Putin and Turkish President Recep Tayyip Erdogan are in Istanbul to mark the completion of a key phase in a natural gas pipeline. The two leaders on Monday are marking the completion of the offshore part of TurkStream’s two lines that will carry natural gas from Russia to Turkey. The lines when finished are expected to supply Russian gas to European markets through Turkish territories. Together the two 930-kilometer (578-mile) lines via the Black Sea will carry 31.5 billion cubic meters (1.1 trillion cubic feet) of natural gas annually. Turkey relies on imports for its energy needs and Russia is its top supplier for natural gas. It bought 28 billion cubic meters last year. That gas is currently transported through another line under the Black Sea and the onshore West Line through Ukraine, which is mired in conflict with Russia.