Despite months of effort, President Bush has not yet convinced most Americans there is justification for U.S. military action to depose Iraqi leader Saddam Hussein, polls show.

"I think a little more diplomacy would be in order," said Creig Crippen, 84, a retired Air Force veteran from Deland, Fla. "I don't like this pre-emptive idea. That's imperial. That's not democratic."

There is widespread support for ending Saddam's rule, but that support is conditioned on proof of a threat from Iraq and on the support of U.S. allies, said a poll released Thursday by the Pew Research Center for the People & the Press.

The poll became public as the United Nations said U.N. inspectors in Iraq looking for evidence of weapons of mass destruction had discovered about 11 empty chemical warheads south of Baghdad.

Two-thirds or more in the Pew poll and other recent polls say they favor military action against Iraq, but only under certain circumstances.

For example, the Pew poll suggested that support for war is strong, 76 percent, if U.N. inspectors find nuclear, biological or chemical weapons in Iraq. The support is evenly split if they find no weapons but determine Iraq has the ability to make these weapons.

The public does not buy the administration's argument that Iraq must prove it does not have these weapons to avoid a U.S. attack. Almost two-thirds, 63 percent, said Iraq's failure to prove it does not have weapons would not be a sufficient reason for a war.

More than half, 53 percent, say the president has not yet explained clearly what's at stake to justify the United States using military force to end Saddam's rule, according to the poll. Some 42 percent say he has.

The number who say Bush has clearly explained what's at stake has eroded since his September address to the United Nations, when it was 52-37 saying he had given a clear explanation.

At the White House, spokesman Scott McClellan said Bush continues to work with other countries on a peaceful solution.

"But if Saddam Hussein will not disarm peacefully and it becomes necessary to disarm him by force, then what we would be doing is not only disarming a real and growing threat, but liberating Iraqi people from a brutal, oppressive regime," McClellan said.

The Pew poll of 1,218 adults was taken Jan. 8-12 and has an error margin of plus or minus 3 percentage points.

"I believe that this is an action that is due because of Saddam Hussein's complete lack of respect for the democratic world and his people," said Philip Pederson, 65, a sales manager from Wheatland, Calif. He is a Vietnam veteran.

Though the president has been making his case against Iraq in earnest since September, White House officials say the heavier lifting doesn't begin until Jan. 28, when Bush delivers his State of the Union address. That's one day after U.N. weapons inspectors issue a preliminary report on what they've found in Iraq.

The drumbeat for war continues Jan. 31, when Bush meets at Camp David with his staunchest anti-Iraq ally, British Prime Minister Tony Blair. If Bush chooses to go to war, whenever that might be, there would be a final, Oval Office address in which he would spell out reasons, White House officials say.

Some in the public will be skeptical no matter what the president tells them about Iraq.

"I think they've made it very clear," said Rachel Wheatley, 23, of Washington, "that they're not really interested in what the inspectors have to say."