The letter of guarantee was due to expire on Monday after SOCAR renewed it by a month in late September.

SOCAR first agreed to buy DESFA in 2013 but the purchase hit a snag when the European Union asked it to reduce the stake to be purchased in the Greek operator on competition grounds.

The deal ran into further complications this year when Greece passed a law raising DESFA's gas tariffs by a lower amount than SOCAR had expected, potentially eating into its future profits.