Exxon sues US government over rights to oil field

The US government and the country's largest oil company are heading for a court showdown over rights to one of the Gulf of Mexico's largest oil finds. ExxonMobil had taken three leases on drilling rights to an oil field worth tens of billions of dollars, but the leases expired in 2008 and the government unexpectedly refused to renew them.

The oil giant says the decision was unprecedented and based on an interpretation of the rules never previously used; the US says oil companies should have leases taken away from them if they do not show genuine plans to develop the oil.

Exxon's partner in the leases is Norway's Statoil, which joined in suing the US Department of the Interior and its secretary Ken Salazar in a Louisiana court this week. Exxon's complaint says the government stands to collect millions of dollars in bonuses and royalties by signing replacement leases.