The Iraqi government has decided to award a contract to develop the prized West Qurna oil field to a consortium led by the U.S. oil company Exxon Mobil.

The Iraqi oil ministry Thursday announced an agreement to give the companies, which include Royal Dutch Shell, a 20-year contract to develop West Qurna.  The field is believed to hold some 8.5 billion barrels of untapped oil.

The Exxon-led consortium has proposed boosting the field's output from its current level of about 280,000 barrels of oil a day up to 2.1 million.

Another consortium, led by Russia's Lukoil, had also competed for the contract.

Iraq has the world's third largest oil reserves, and has been trying to boost production.  Oil sales account for the vast majority of the government's revenue.

Earlier this week, Iraq finalized a deal with the British oil company BP and China's CNPC to develop the giant Rumaila oil field.

Some information for this report was provided by AFP, AP and Reuters.