WASHINGTON -- A provision that would allow an inventory of offshore oil and gas deposits was adopted into comprehensive energy legislation early Tuesday morning as a final version of the bill won the approval of a House-Senate committee, usually a good harbinger for passage.

Though the provision allows only for seismic testing, many view the inventory as a first step toward future drilling off the South Carolina coast -- something local officials say has potentially dire consequences for tourism and the environment.

Rep. Joe Wilson, R-S.C., said he would support the energy bill in the House, even with the offshore inventory provision.

"My position is to oppose offshore drilling off of South Carolina's coast," Wilson said. "And, indeed, the energy bill provides for an inventory, but there is no provision for actual drilling."

The original House-passed version of the bill, which Wilson supported, contained no language on offshore resource inventories. But when the issue was taken up by House and Senate conferees, negotiators were able to keep committee members from California, North Carolina and Florida from stripping the provision from the bill.

Both South Carolina Republican Sens. Jim DeMint and Lindsey Graham voted for a failed amendment that would have removed the offshore inventory language from the original legislation. But both eventually supported the final Senate version of the bill, which included the offshore inventory provision.

A spokesman for Sen. Lindsey Graham, R-S.C., said the senator "will be reviewing the conference report this week, and he hopes that it's something he can support."

Experts speculate that most of the oil and natural gas deposits are located in an area off the Atlantic coast called the Carolina Trough, a large undersea basin that runs from North Carolina to northern Georgia. The trough gets closest to shore near Cape Hatteras, N.C., where it is estimated to be about 60 miles from the coast.

Near Hilton Head Island, the trough is estimated to be about 150 miles from shore, said Deborah Hutchinson, research geologist for the U.S. Geological Survey.

Because the prospective deposits are located so far from shore, it's difficult to determine what impact drilling might have on the immediate coastal areas.

While no drilling could begin until at least 2012 -- the year a federal moratorium on offshore drilling expires -- geophysical testing and exploratory work could begin as soon as the bill is passed. Experts, however, say it's likely to be at least a year before actual testing commences.

The chairman of the Energy and Commerce committee, Texas Republican Rep. Joe Barton, said he expects the final version of the energy bill to be up for vote in both the House and the Senate by the end of the week. The committee-passed bill still needs to gain approval in both houses and be signed by President Bush to become law.