Energy companies have placed US$487.3 million in winning bids for the right to drill in the western Gulf of Mexico, knowing that they may get a chance later to also explore in other areas that have been off limits for decades.

The lease sale Wednesday was the first to take place since US president George W. Bush last month lifted an executive ban on oil drilling off the Atlantic and Pacific coasts.

offshore exploration

Since then, politicians in both parties have signalled that they are willing to expand offshore exploration.

Interior Secretary Dirk Kemp-thorne called Wednesday's sale a step toward more domestic oil production.

He acknowledged, however, that some of the purchased leases may not end up producing oil.

Offshore wells now provide 27 per cent of the United States' domestic oil.