US bid winners Occidental Petroleum Corp, Amerada Hess Corp and ChevronTexaco were among more than 120 companies that registered bids or expressed interest in the offers, Libyan officials said.

A total of 15 licences were offered for onshore and offshore blocks in one of the world's exploration hotspots.

The contracts to American firms follow the easing of a trade embargo on oil-rich Libya by the United States last spring after Tripoli gave up weapons of mass destruction.

Tripoli's ties with the West were also helped by its agreement in 2003 to accept civil responsibility and make payouts for the 1988 Lockerbie bombing of a Pan Am airliner over Scotland that killed 270 people.

Ambitious plans

Libya produces about 1.6 million barrels per day and hopes to raise this to 2.1 million bpd by the end of this decade.

A member of the Opec oil producing cartel, Libya says it hopes to attract $30 billion of investments up to 2010.

During the 1970s and 1980s, foreign energy companies flocked to Libya, despite Tripoli's hardline anti-Western stand, but in 1986 the United States imposed an embargo on dealings with the country, which it accused of sponsoring terrorism.

In 1992, the United Nations imposed economic sanctions in the wake of the Lockerbie bombing, blamed on Libyan intelligence.

But the UN sanctions were removed after Tripoli agreed to pay compensation to the families of the Lockerbie victims.

The US embargo was lifted after Libya renounced weapons of mass destruction a year ago.