Oil companies replaced only 58 percent of the U.S. crude they drilled with new reserves in 2003, according to the U.S. Energy Information Administration.

Total U.S. crude oil reserves stood at 21.891 billion barrels at end of 2003, down 3.5 percent from the year before, the Energy Department's analytical arm said.

The amount of crude oil discovered last year totaled 1.232 billion barrels, 30 percent more than 2002's discoveries of 946 million barrels, the EIA said.

However, that was not enough to offset the amount oil that was drilled.

The majority of those finds were from new offshore fields in the Gulf of Mexico, while the north slope of Alaska, normally a major contributor to new oil supplies, "had no significant impact" on total U.S. oil discoveries in 2003, the agency said.

The new report could figure in the ongoing political debate over whether to open Alaska's Arctic National Wildlife Refuge to oil drilling.

President Bush wants to open the wildlife refuge, which may contain up to 16 billion barrels of crude, as a key plank in his energy plan. Democratic presidential challenger John Kerry joined a coalition of Democrats and moderate Republicans in the Senate to block drilling in the refuge.

Kerry contends the United States should instead develop alternative energy sources and impose stricter fuel efficiency standards on vehicles to cut U.S. crude imports from the volatile Middle East.

In contrast to oil, U.S. natural gas reserves increased 1.1 percent to just over 189 trillion cubic in 2003, rising for the fifth year in a row, the EIA said.

Total discoveries of dry gas reserves last year were 19.286 trillion cubic feet, up 8 percent from 2002, the EIA said. New gas reserves replaced 111 percent of natural gas production in 2003, the agency said.

Most of the gas discoveries came from existing fields in the Rocky Mountain states and Texas, the EIA said.