A ban on drilling in most California waters has been in effect for several years

MONTEREY, California (CNN) -- President Bill Clinton on Friday will extend to 2012 a moratorium on most offshore oil drilling. The announcement -- sure to please environmentalists and anger the oil industry -- will come during Clinton's speech before the National Ocean Conference here in Monterey, White House officials confirmed.

Clinton is also to announce a permanent drilling ban covering 12 sanctuaries around the nation, including four in California, Deputy White House Press Secretary Joe Lockhart said.

The oil industry has pressed the Clinton administration not to extend the drilling moratorium.

Environmentalists welcomed Clinton's move.

"It should be extended to Alaska and to the rocky shores of Maine, and to the Florida Keys," said Warner Chabot, of the Center for Marine Conservation. "But it's a great first step." ( 170K/15 sec. AIFF or WAV sound)

Drilling controversy erupted 3 decades ago

North America leads the world in the number of oil drilling platforms -- about 3,100.

But the number of drilling platforms has been on the decline in recent years, partly due to concern over the impact oil and gas drilling has on marine life.

An oil-covered bird during the great oil "blow out" of 1969

Oil and gas leasing and drilling are prohibited on most of the federal outer continental shelf, excluding the Gulf of Mexico and part of the waters off Alaska.

Many officials from coastal states oppose offshore drilling because of the risk of oil spills that can ruin beaches.

Environmentalists want offshore drilling to stop, in order to protect the oceans from further pollution.

Controversy over offshore drilling first surfaced in the United States in 1969, after a cracked sea floor led to a huge oil spill off Santa Barbara, California.

During the 1970s, when many Arab nations launched an oil embargo, many U.S. officials pushed for the exploration of offshore drilling sites off U.S. shores.

Environmentalists responded by turning up the volume on their cries against offshore drilling.

Voting against drilling

Concerns about the marine ecosystem have cut the number of oil platforms

By the 1980s, the issue began appearing on ballots.

California voters in 26 coastal communities passed initiatives which provided no zoning to accommodate onshore facilities for companies pursuing offshore development.

The state later put a permanent ban on oil drilling in its waters, with two exceptions: areas off Santa Barbara and Orange County, due to pre-existing leases.

The moratorium Clinton is extending was established by his predecessor, President George Bush, and expires in 2002. The presidential moratorium is separate from a year-to-year moratorium imposed annually by the U.S. Congress since 1981.

Correspondent Jennifer Auther and Reuters contributed to this report.