The U.S. offshore oil drilling ban will reduce crude output by an average of 82,000 barrels per day next year, more than previously estimated, the government's top energy forecaster said on Wednesday.

The Energy Information Administration had said last month that the moratorium, which the government put on exploration rigs in response to the BP Plc oil spill, would reduce next year's U.S. crude output by an average of 70,000 bpd.

In May, Interior Secretary Ken Salazar put a six month moratorium on deep water exploration rigs.

The moratorium will delay deep water projects, the effect of which will speed up late in 2011, the EIA said.

The reductions in crude oil production increase from a monthly average of about 10,000 bpd in September 2010 to nearly 100,000 bpd by December 2011, the EIA said in its monthly short term energy outlook.

The moratorium will help push U.S. overall crude output lower next year, the EIA said, reversing a pattern of increases that had occurred over several years. Next year U.S. oil output should fall an average of 26,000 bpd to 5.37 million bpd.

During the fourth quarter this year an average of 31,000 bpd of oil output will be lost, compared with last month's estimate of 26,000 bpd, the EIA said.

The ban was blocked by a federal court late last month. But a U.S. appeals court will consider the Obama administration's request to keep the moratorium on Thursday.

The administration is expected to unveil a new, more flexible, moratorium in the next few days that could allow drilling in certain subsea fields.

(Reporting by Timothy Gardner; Editing by Marguerita Choy)