US Bush said yesterday he had ordered a reversal of an executive ban on oil and natural gas drilling in offshore US waters, adding it was now up to Congress to turn his decision into law. With this decision, he undid one of the greener achievements of his father when the latter had been president.

''`Today I've taken every step within my power to allow offshore exploration of the OCS (Outer Continental Shelf),'' Bush said in a statement at the White House. ''This means the only thing standing between the American people and these vast oil resources is action by the US Congress.''

Reversing the executive branch's moratorium, which was widely expected, is not expected to have much impact unless Congress heeds Bush's call to change existing legislation. Much of the Democratic-controlled Congress is opposed to such drilling.

Pressure to permit drilling off the Pacific and Atlantic Ocean coastlines and in the Eastern Gulf of Mexico has been building as oil and gasoline prices have surged to records. However, opinions have been mixed considering the adverse environmental effects of such drilling operations.

Not all the opposition has been partisan and Democratic; Arnold Schwarzenegger, California's Republican governor, opposes it, as do many East Coast governors.

Congress has barred drilling since 1983 through an annual Interior Department spending bill. That ban could be lifted if Bush refused to sign the department's fiscal 2009 appropriations measure that is now being debated in the House and Senate. The president's father, George H W Bush, had imposed the existing executive moratorium.

About 17.8 billion barrels and 76 trillion cubic feet of gas are off-limits to drilling as a result of the Congressional and presidential moratoria, according to the Minerals Management Service, an agency of the US Interior Department.

Democrats say instead the government should push oil explorers to drill more on existing permits and find other ways to reduce dependence on foreign oil imports. On Monday, the campaign of Democratic presidential candidate Barack Obama said offshore drilling "would merely prolong the failed energy policies we have seen from Washington for 30 years."

"If offshore drilling would provide short-term relief at the pump or a long-term strategy for energy independence, it would be worthy of our consideration, regardless of the risks. But most experts, even within the Bush Administration, concede it would do neither," said the senator's campaign staff in a statement released before Bush's news conference.

In this issue, he finds himself at odds with his likely rival for the presidential elections, Republican Senator John McCain. Also, the decision to lift the ban was quickly applauded by industry groups including the US Chamber of Commerce and the American Chemistry Council, which say their members are suffering from escalating energy prices.