WASHINGTON (AP) -- The White House said Friday that chemical warheads found in Iraq had not been declared by Saddam Hussein's government as required by U.N. rules, and called the discovery ``troubling and serious.''

Presidential spokesman Ari Fleischer stopped short of calling the weapons cache a breach of an anti-arms U.N. resolution, saying the United States has already found Saddam in violation of several U.N. rules.

U.S. officials hope the discovery of 11 empty chemical warheads at a storage area 75 miles south of Baghdad will bolster their case against Saddam. Iraq said the weapons were on its 12,000-page declaration required by the U.N., an assertion disputed by Fleischer.

``Chemical warheads were not, not on the ... list of weapons Iraq issued,'' he said. ``The fact that Iraq is in possession of undeclared chemical warheads ... is troubling and serious.''

He repeated the line when asked if the discovery represented the long-sought ``smoking gun'' against Saddam.

Fleischer also dismissed Saddam Hussein's claim Friday that Iraqi enemies would face ``suicide'' at the gates of his capital if an attack were launched.

``We are much less interested in Saddam Hussein's talking and much more interested in Saddam Hussein's disarming,'' Fleischer said.

Sen. John Kyl, R-Ariz., says that if Iraq had not declared the warheads, they would be in ``material breach'' of U.N. resolutions -- meaning there could be grounds for use of force.

``That is a big deal,'' Kyl said, adding that it would only be the tip of the iceberg. ``There's a whole lot more we're never likely to find because it's too hard to find in a country as large as Iraq.''

Though Fleischer stopped short of labeling the discovery a ``material breach,'' which Bush and the United Nations could use as justification for war, the press secretary said it ``doesn't get them out of material breach.''

He added that Iraq is barred from possessing chemical weapons.

``Iraq's statement here is they forgot that they had these chemical weapons ... which raises the question of what other memory lapses they have which could ... bring harm to their neighbors or our allies,'' he said.

State Department spokesman Richard Boucher said the U.N. inspectors have indicated that Iraq has failed in a number of areas to cooperate fully with Security Council requirements.

``There's no point in continuing forever, going on, if Iraq is not cooperating,'' Boucher said.

The Pentagon continued its war preparations, saying it might dispatch three more aircraft carriers to the region.

By stationing carriers in the Persian Gulf, the Red Sea and the Mediterranean Sea, Navy fighter-bombers would be in position to attack from three directions, complicating Iraq's effort to defend its airspace.

The administration believes that a U.N. blessing is not necessary and is prepared to take action without it if circumstances warrant, in concert with like-minded countries.

A potential turning point in the Iraq debate could occur starting Jan. 27, when U.N. inspectors are due to report to the Security Council.

Secretary of State Colin Powell will confer with fellow Security Council members during a visit to the United Nations on Sunday and Monday.

Most European nations oppose a military attack against Iraq without the endorsement of the Security Council.

A senior administration official, speaking to reporters in Germany on Thursday on condition that he not be identified, said countries that support that view only encourage Saddam not to cooperate with the inspectors.

European Union foreign policy chief Javier Solana has said he cannot see how a war against Iraq can start without clear evidence that Iraq pursues biological, chemical and nuclear arms -- all forbidden by the United Nations.

He has not said what his position would be if such evidence were uncovered.

The chief U.N. weapons inspector, Hans Blix, has spoken of a second deadline of March 27, citing an earlier U.N. resolution.

Some U.S. officials favor disregarding the March 27 deadline, believing critics will use it as an excuse to delay a confrontation with Iraq.