Secretary of State James A. Baker III told Iraq yesterday that time has started to run out on the 15 days during which he is prepared to visit Baghdad for talks with President Saddam Hussein, and President Bush reportedly told a congressional delegation that Saddam must understand that "if we get into an armed situation, he's going to get his ass kicked."

Bush's blunt language was quoted by Rep. Elton Gallegly (R-Calif.), following a meeting at the White House in which he and other members of Congress reported on a trip to the Persian Gulf. Other members of the delegation said they were struck by Bush's determination to see Iraq pushed out of Kuwait.

The Defense Department, meanwhile, sought to minimize statements Wednesday by a top U.S. military commander in the gulf that American-led forces will not be ready for combat by the Jan. 15 deadline imposed by the United Nations Security Council.

Pentagon officials accompanying Defense Secretary Richard B. Cheney on a visit to Riyadh, Saudi Arabia, said that Air Force and Navy warplanes will be prepared to attack Iraqi positions by Jan. 15 even if some U.S. ground units in the region are not fully operational. {Story on Page A32.}

White House Press Secretary Marlin Fitzwater played down the remarks about American readiness, saying it "doesn't cause us any grief to have a little uncertainty in the mind of Mr. Hussein about when exactly we might choose to enforce the U.N. sanctions."

At a news conference here, Baker made what U.S. officials called a last-ditch attempt to emphasize that failure to have a meeting would move Iraq inexorably toward the threat of war if it does not withdraw from Kuwait by Jan. 15.

"This is the 20th of December," Baker said. "It is the first of the 15 days that the president has offered for us to go to Baghdad and have a meeting. We hope very much that Iraq will choose to pick up on one of these dates because we believe that if they don't, they perhaps could regret it later."

Baker added that he will interrupt a vacation, planned to begin today, and go to Baghdad "on a moment's notice" if Saddam agrees to discuss a peaceful resolution of the gulf crisis.

Last month, Bush proposed that Iraqi Foreign Minister Tariq Aziz should come here for a White House meeting and that Baker should follow with a trip to Baghdad in an effort to convince Saddam that the administration is prepared to use force if Iraqi forces are not out of Kuwait by Jan. 15.

However, Iraq's subsequent responses have been dismissed by U.S. officials as stalling aimed at buying more time or as attempts to turn a meeting between Baker and Saddam into negotiations on Iraqi demands that the United States refuses to consider.

Bush finally served notice on Baghdad that Baker would be available to go there any time in the 15-day period from yesterday to Jan. 3. This U.S. proposal was reiterated in a message delivered to Baghdad earlier this week, but U.S. officials said yesterday that in two subsequent meetings with Joseph C. Wilson IV, acting head of the U.S. Embassy in Iraq, the Iraqis still had not mentioned any dates.

Baker is scheduled to travel to Houston today and then to an undisclosed vacation spot. Unless the Iraq trip gets a green light, he tentatively does not plan to return here until after Jan. 1.

In his comments yesterday, Baker gave what U.S. officials said was a broad hint that to simplify matters, the United States would be willing to call off the proposed visit here of Aziz or possibly reverse Bush's original proposal and have Aziz come here after Baker goes to Baghdad. Asked whether it is still necessary for Aziz to come here first, Baker replied: "Well, that's what the president had in mind, and I think the president thinks that would be useful."

Later, however, senior U.S.

officials, who declined to be identified, said Baker's answer was intended to give the United States flexibility to cancel the Aziz part of the exchange if that would help in getting the secretary of state to Baghdad.

According to the officials, a face-to-face meeting between Baker and Saddam always has been considered the crucial element of the U.S. proposal, and they said the invitation for Aziz to come here had been included to give the Iraqis a sense of parity in the arrangements.

At one point yesterday, Baker alluded to Aziz's visit to Moscow last month and said Saddam should have no doubt of Soviet support for the U.N. resolutions "if he had a faithful rendition from Aziz of the meeting in Moscow." The officials characterized Baker's remark as a reflection of the U.S. view that Aziz, like other Iraqi officials, is afraid to tell Saddam things he doesn't want to hear and that Baker is the only one who might be able to convince Saddam of Bush's resolve to use force if necessary.

The officials said they no longer have much hope that Saddam will agree to meet Baker, but they added that the administration is determined to keep that avenue open as long as possible. Many U.S. officials are expecting what they call "a January surprise" between Jan. 3 and Jan. 15 in which Saddam would give a conditional invitation to Baker or make some other move such as partially withdrawing from Kuwait in hopes of stalling a showdown beyond the U.N. deadline.

After the meeting with House members, Rep. George "Buddy" Darden (D-Ga.) said the president had told the group he had "crossed the Rubicon" in his gulf policy, but a White House spokesman said later that Bush has not made "a decision to attack."

"My sense of things is he's very impatient," said Rep. Michael R. McNulty (D-N.Y.). He added that Bush appeared to believe "the clock was ticking and he was going to make his decision in the near future."

Gallegly said Bush's blunt language about Saddam came as part of a discussion in which the president indicated that the best hope for peace is to convince Saddam that he is up against overwhelming odds. "It was not a Rambo-type comment," Gallegly said.

Senate Majority Leader George J. Mitchell (D-Maine), who returned early yesterday from his own Mideast trip, said he and other senators had told leaders in Saudi Arabia, Egypt and Israel that the United States is united behind Bush's goal of complete Iraqi withdrawal from Kuwait.

Mitchell said congressional leaders "are considering" a resolution supporting the use of force in the gulf, but he added that the form and timing would depend on such events as whether direct U.S.-Iraqi talks take place. But he said a "blank check" resolution authorizing

the use of force could not pass today.

He also reiterated his position that the United States "should continue the policy of {economic} sanctions against Iraq."

Mitchell, who also met with Bush at the White House late yesterday, said he was particularly concerned that a war in the gulf would quick- ly result in an Iraqi attack on

Israel, which he said could easily shatter the Arab coalition now aligned with the United States against Saddam.

Bush also met yesterday with Presiding Episcopal Bishop Edmond L. Browning, who said he told the president that he hopes war can be avoided and urged him to provide the moral leadership that could

lead to a breakthrough in the Mideast.

Browning, leader of Bush's church, said the president asked him, "How can we morally not do anything?" Staff writer Tom Kenworthy contributed to this report.