WASHINGTON--President Bush froze Iraq's assets in this country and cut off imports of 588,000 barrels a day of Iraqi oil yesterday in retaliation for the lightning invasion of Kuwait. U.S. officials were seeking word on American oil workers missing in the region.

Kuwait's ambassador appealed for American military help for his country but none was forthcoming, at least for the moment. Bush said, "We're not ruling any options in but we're not ruling any options out."

A State Department official disclosed that the invading Iraqi troops rounded up and moved "a few" American oil field workers from just inside Kuwait's border. He said their whereabouts were not known.

"We are making every effort to make inquiries and find out more," said the official, who commented on condition he not be identified.

Naked Aggression

The president, in blocking virtually all commerce with Iraq, denounced its "naked aggression" against a small neighbor. Some members of Congress compared Iraqi leader Saddam Hussein to Hitler and said they believed the American people would accept higher fuel prices resulting from an attempt to strangle Iraq economically.

Bush flew to Aspen, Colo. to deliver a speech appealing for keeping America strong enough militarily to respond to terrorism, hostage taking and "renegade regimes and unpredictable rulers."

He said Iraq's "brutal aggression" made his point--that despite the lessening of the Soviet threat in recent months, "threats can arise suddenly, unpredictably, and from unexpected quarters."

Bush conferred in Colorado with the vacationing British prime minister, Margaret Thatcher. He arranged to return to Washington earlier than planned and abandoned hopes for a restful weekend at the presidential retreat at Camp David, Md.

Thatcher, referring to Saddam, said, "We find his behavior intolerable." She called for collective action by the member states of the United Nations.

Bush said he conferred by telephone with Egyptian President Hosni Mubarak and other Arab leaders, and said he was encouraged by their efforts to find an "Arab answer" to the problem.

Before leaving Washington, Bush said the United States would do whatever more is necessary "to defend our longstanding, vital interests" in the Persian Gulf. He said he and his advisers would "consider all possible options available to us."

But he wasn't specific and said he wasn't discussing military intervention--a course which experts said offered no easy choices to him. He added that he wouldn't talk publicly about military options in any event.

"We don't stand a chance if we don't get any aid from our friends," a dismayed Ambassador Saud Nasser Al-Sabah told reporters. "U.S. intervention at this stage is of paramount importance."

As an alternative, Bush took one of the toughest economic options open to him. He froze control of Iraqi assets in the United States--and of Kuwait's assets, too, so they wouldn't fall into Iraqi hands.

And he halted commerce between the United States and Iraq, a nation that normally provides the United States with 588,000 barrels of oil a day--7.6 percent of U.S. imports.

Administration officials said they could not estimate the value of Kuwaiti and Iraqi assets affected by the freeze, but one Treasury official described them as "significant."

After a morning of closed briefings, Sen. David Boren (D-Okla.), who chairs the Senate Intelligence Committee, said if Iraq headed for Saudi Arabia and its oil fields just 250 miles across the desert, "I think it would be a direct threat to the security of this country."

Saddam must calculate whether his nation, weary from its long war with Iran, is willing to support further miltary adventures, Boren said. A possible invasion by Iraq of Saudi Arabia "cannot be ruled out," he said.

And Sen. Lloyd Bentsen (D-Texas) expressed fear that if the Iraqi takeover of Kuwait succeeds "Saudi Arabia might be next--and then Saddam Hussein would have a stranglehold on the West's oil supply."

The Texan said the United States should seek a worldwide embargo against Iraqi oil. "Iraq is deeply in debt and very dependent on oil revenues and such an embargo would be an effective way to get their attention," he said.

Reflecting the anger boiling up on Capitol Hill, Rep. Ike Skelton (D-Mo.) told the House, "The attack is a financial assault on America and on the rest of the world that is dependent on Mideastern oil."

The House gave speedy 416-0 approval to a pending economic sanctions bill aimed at Iraq. The measure would cut off Iraq's $200 million a year in Export-Import Bank credits and tighten restrictions on U.S. exports that could have military as well as civilian uses.

Pentagon sources also said an evacuation of 3000 Americans, mostly business people, from Kuwait was under consideration. About 130 are U.S. employees.

The State Department said U.S. Embassy personnel were safe and the embassy grounds had not been penetrated during the fighting, but it advised Americans to postpone travel to Kuwait.

The aircraft carrier Independence and a six-ship battle group had been given high-speed authority to head toward the region from the Indian Ocean but were several days from reaching a "striking distance" position outside the Persian Gulf, Pentagon sources said.