President Bush is ordering more than 150,000 additional American troops to the Persian Gulf, a move that nearly doubles U.S. firepower in the region and marks a fundamental shift toward an offensive military stance.

Bush said Thursday in announcing the new wave of troop deployments for Operation Desert Shield that he still hoped to get Iraq out of Kuwait without starting a war. But he said he wanted an "adequate offensive military option" in case United Nations economic sanctions and diplomatic pressures against Iraq prove futile.Analysts said the move brought the United States closer to war with Iraq.

"The Iraqis, in effect, are being put on notice that they will be attacked" unless they withdraw from Kuwait under Bush's terms, said Frank Gaffney Jr., director of the Center for Security Policy and a former Pentagon official.

The scale of the additional U.S. troop deployments is enormous. Once the added forces are in place, America will have more troops in the gulf region than it had in Europe during the Cold War when the perceived enemy was a nuclear superpower. About one-third of the Army's worldwide force will be in the Saudi desert.

About 230,000 U.S. air, ground and sea forces now are in and around Saudi Arabia, and a coalition of other Western and Arab nations have put at least 100,000 troops in the gulf area. The Iraqi force in Kuwait and southern Iraq is estimated at 430,000.

Full deployment of the units listed Thursday by Defense Secretary Dick Cheney, who gave details of the new buildup, would add more than 150,000 troops to the U.S. forces there, Pentagon officials said in private conversations.

Bush and Pentagon officials refused to disclose the numbers, but the new deployment should more than double the number of U.S. tanks in Saudi Arabia, to about 2,000, judging from organization charts and estimates by Army sources.

The Pentagon estimates that Iraq has about 3,500 tanks in andaround Kuwait.

Bush said he hoped Iraqi President Saddam Hussein viewed the stepped-up U.S. deployments to the gulf as evidence that the Western and Arab coalition arrayed against him was serious about using military force if diplomatic and economic pressures fail.

"If this movement of force is what convinces him, so much the better," Bush said. He added later, "When he surveys the force that's there . . . he will recognize that he is up against just a foe that he can't possibly manage militarily."

The president also said he was heartened by reports from Secretary of State James A. Baker III that the Soviet Union would not oppose passage of a U.N. resolution authorizing the use of force against Iraq as a last resort to liberate Kuwait.

Administration officials had strongly hinted in recent weeks that additional U.S. Army units would be sent to Saudi Arabia, but there had been little indication that Bush would order such a large increase in naval and Marine power.

Sen. Claiborne Pell, D-R.I., chairman of the Senate Foreign Relations Committee, expressed skepticism about the buildup.

"I am concerned that the administration is moving to establish an offensive capacity in advance of a U.N. resolution authorizing offensive action," Pell said. He said the international trade embargo against Iraq has not had "a decent chance to produce results."