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.