US oil company Transocean Sedco Forex has bought R&B Falcon Corporation for $8.8 billion (€9.75 billion), a deal that will forge the world's largest offshore oil drilling firm.

"The acquisition of R&B Falcon creates a new offshore drilling company that is a worldwide leader," said Mr Victor Grijalva, chairman Transocean.

R&B Falcon's 139 mobile offshore drilling units and marine barges will complement the 72-rig Transocean offshore fleet.

The new company would be the world's number three in oil industry services, with an equity market capitalisation of $17.7 billion.