WASHINGTON (AP) _ Acting within hours after government approval, Exxon and Mobil formally sealed their $81 billion merger Tuesday, creating the world's largest privately owned oil company.

The Federal Trade Commission approved Exxon's acquisition of Mobil after requiring that the new company sell more than 2,400 service stations, a refinery and other assets to ensure continued competition.

Company officials immediately registered the new Exxon-Mobil in Delaware where Mobil was registered and New Jersey where Exxon was registered, formally creating the new oil giant, said a company spokesman.

``We have completed the merger,'' said Exxon-Mobil spokesman Robert Lanyon.