HOUSTON (AP) — The national debate over opening more offshore areas to oil and gas exploration has begged the question: Just what are the companies doing with the tens of millions of acres they're already leasing from the federal government?

In particular, congressional Democrats who oppose President Bush's plan to expand offshore drilling point to 68 million acres of federal land and offshore sites now leased by oil companies that sit idle.

The 68 million acres under lease to oil companies has potential reserves to nearly double U.S. oil production and increase natural gas output by 75 percent, the Democrats claim.

So why the lack of activity, particularly when oil prices are at historic levels?