"The contract is worth $16 billion," Ali Vakili, director of POGC told the official IRNA news agency. "Some $6 billion is for development of offshore and $10 billion for development of onshore gas fields for a period of 25 years."

Iran's Oil Minister, Gholam Hossein Nozari, said the deal was a vindication of his country's efforts to counter pressures to isolate his nation. "This is the biggest investment contract in the country's energy sector," the official IRNA news agency quoted Nozari as saying.

The multibillion dollar contract was signed weeks after China's biggest oil refiner, Sinopec, and Iran signed a $2 billion agreement on developing the Yadavaran oil field. That agreement, coinciding with US-led efforts to pressure Iran with threats of tighter economic sanctions to rein in Tehran's nuclear program, drew a sharp rebuke from Washington.

The reserves at the Golshan gas field, 65 kilometers from the southern port city of Bushehr, is estimated more than 50 trillion cubic feet of gas and it is expected to produce 2.5 billion cubic feet of natural gas per day.

The Ferdows' gas reserves is estimated at around 10 trillion cubic feet and it would produce more than 880 million cubic feet of gas on a daily basis.