BAGHDAD - Iraq on Tuesday formally signed a deal worth 14 to 20 billion dollars with Britain's BP and China's CNPC to almost triple production at a giant southern oilfield.

The venture is expected to boost production at the southern Rumaila field from the current one million barrels per day to around 2.8 million bpd over its 20-year duration.

Rumaila is already integral to Iraq's oil output, contributing almost half of the nation's current production of around 2.5 million bpd, and is estimated to have further reserves of 17.7 billion barrels.

BP and CNPC are projected to invest 14 to 20 billion dollars between them and the companies have agreed to accept payment of two dollars per additional barrel produced at Rumaila.

The Iraqi cabinet approved the contract two weeks ago.