The Bush administration is waiting for a clear pattern of violations by Iraq before pursuing a showdown in the United Nations, even as allied warplanes come under repeated attack.

Secretary of Defense Donald H. Rumsfeld called Iraq's no-fly-zone firing unacceptable. But he also said Monday, "It's up to the president and the U.N. Security Council on their view of Iraq's behavior over a period of time, and those discussions have just begun."

White House deputy spokesman Scott McClellan condemned the Iraqi attacks — at least four in the past few days — as "a violation that would constitute a material breach" of the resolution adopted unanimously by the council Nov. 8 to force Iraq to disarm.

But McClellan, like Rumsfeld, indicated the administration was not taking its complaint to the council, which threatened Iraq with consequences in the event of breaches of U.N. resolutions.

"We have that option," the spokesman said, indicating that a decision had not been made by President Bush. The president repeatedly has threatened President Saddam Hussein with war if he reneges on his assurance that he will comply with U.N. orders to get rid of weapons of mass destruction.

By holding off, the administration defers a potential confrontation with U.S. allies. They were reluctant in the first place to threaten Iraq with force if it did not admit international inspectors and disarm, and they are still disinclined to attack Baghdad.

It also gives the United States and Britain new opportunities to respond to attacks on patrolling aircraft by bombing Iraqi installations.

The United Nations has kept at arm's length from the overflights, which began over northern Iraq after the 1991 Persian Gulf War to protect Kurds and later over southern Iraq to shield the Shiites there.

The U.N. position is that the United States and Britain, not the world organization, made the decision to ban Iraqi warplanes from the areas and to enforce it by patrolling the no-fly zones.

But the U.N. Security Council has committed itself to the search for hidden chemical, biological and nuclear weapons programs. Chief U.N. inspector Hans Blix and Mohamed ElBaradei of the International Atomic Energy Agency arrived Monday in Baghdad with technical experts to lay the groundwork for inspections that are to begin a week from Wednesday.

Iraq has until Dec. 8 to provide inspectors and the Security Council with a complete list of all parts of chemical, biological and nuclear weapons programs.

Any Iraqi resistance could produce an instant showdown, but Rumsfeld has said that while it was unacceptable for Iraq to fire at U.S. and British warplanes in the no-fly zones, first "a pattern of behavior will evolve and then people will make judgments with respect to it."

"These discussions have just begun," Rumsfeld said Monday in Santiago, Chile, as he prepared for talks on security with officials from Chile, Colombia, Brazil and Argentina.

Since the Security Council approved tough inspections and threatened "serious consequences" for defiance, Iraq has fired at least four times on U.S. or British planes. The allies responded with several attacks in both the northern and southern zones.

And in another sign of defiance, an Iraqi fighter jet penetrated about 50 miles into the southern zone Monday, the Pentagon said. There were no U.S. or British jets close enough to respond before the Iraqi warplane escaped, an official said.

McClellan noted the Security Council has insisted that Iraq "not take or threaten hostile acts directed against any representative or personnel of any member state taking action to uphold any council resolution."

However, the spokesman said, "I think we are jumping a little bit ahead here. Let's see what happens Dec. 8."

The spokesman did not cite a resolution authorizing the overflights, and Russia and several other members of the Security Council maintain it never authorized the flights.

Meanwhile, Iraq protested in a letter circulated Monday in the Security Council that U.S. and British warplanes had violated Iraqi airspace 1,055 times in a month through Oct. 17. Foreign Minister Naji Sabri said in the letter Iraq had a "right to defend itself against this ongoing, hostile, terrorist activity."

Secretary of State Colin Powell said there could be a heightened threat of terror if the United States attacked Iraq. "It's a risk we'll have to take and we'll have to prepare ourselves for it if it comes," he said.

If Iraq cooperates with the inspections "there is a possibility of a peaceful solution," Powell said. "If it does not, then force of arms will be required."