American requests for help in the event of war with Iraq are designed to show the nation's seriousness of purpose, Defense Secretary Donald H. Rumsfeld said Tuesday.

He said about 50 countries around the world had been approached for help by message or by U.S. diplomats in their capitals. President Bush lobbied NATO allies at a summit last week.

"Some have said they will help a lot, some have said a little," Rumsfeld said. "Some have asked that what they are prepared to do be kept confidential."

He declined to say whether Russia or Arab countries were among the countries approached.

Behind the effort was the Bush administration's determination "to make sure the Iraqi regime is aware of our seriousness of purpose," Rumsfeld said.

As U.N. weapons inspection teams prepared to go to work in Iraq, Rumsfeld told a group of international reporters that what happens next is in the hands of the United Nations.

"It is up to the Security Council to make judgments," he said, on whether Baghdad is found in major violation of U.N disarmament demands. The council has warned of "serious consequences" for Iraq if violations are found.

The administration has threatened military action against Iraq in that case, with or without U.N. sanction.

Appearing with Rumsfeld, Air Force. Gen. Richard Myers, chairman of the Joint Chiefs of Staff, said U.S. forces were prepared for any contingency and "this readiness is not tied to any particular date."

At the White House, spokesman Ari Fleischer said nothing the United States has seen from Iraq changes President Bush's thinking that Saddam Hussein's government is a serious threat to world peace.

He said Iraq had until Dec. 8 to list the weapons of mass destruction it possesses and then "that will begin a process where we find out whether the Iraqis told the truth or not."

Asked what would happen if Iraqis did not cooperate in the first inspection set for Wednesday, Fleischer said Bush has announced a policy of zero tolerance.

"And Saddam Hussein will have to figure out exactly what zero tolerance means," he said.

A Pentagon spokesman, Lt. Col. Dave Lapan, disputed a report by the official Iraqi news agency that air defense units fired at American and British warplanes in the no fly zones.

Lapan said no Iraqi attack was detected in either zone on Tuesday. Coalition aircraft did not fly over the northern zone and patrols over the southern zone were unhindered, he said.

The Iraqi agency, quoting an unidentified military spokesman, said warplanes flying from bases in Turkey carried out 16 sorties in the northern zone. It said aircraft taking off from bases in Kuwait carried out 29 sorties in the southern zone.

The no-fly zones were set up in the past decade to protect Kurds in the north and Shiite Muslims in the south from Iraqi government forces. Iraq does not recognize the zones and routinely challenges the U.S. and British aircraft patrolling them.