Mobil Corp., Chevron, Unocal Corp. and Conoco Inc., four of the largest U.S. oil companies, announced price freezes on gasoline late Wednesday after the start of war in the Middle East.

The nation's oil industry came under sharp criticism for a rapid round of price increases at the pump in the immediate aftermath of Iraq's Aug. 2 invasion of Kuwait. President Bush urged the industry to show moderation on pricing and the industry complied by temporarily holding the line on gas prices.In Fairfax, Va., Mobil said it was imposing an immediate freeze on the prices it charges for gasoline and all other petroleum products it sells in the United States.

Mobil Chairman Allen E. Murray said the action by the nation's No. 2 oil company was "a show of support for American policy and a demonstration of our determination to do our part in the national effort."

Murray said Mobil's petroleum prices would remain at prewar levels "until further notice."