Most Americans favor using nuclear weapons against Iraq if Saddam Hussein attacks U.S. military forces with chemical or biological weapons in a war that the public believes is virtually inevitable, according to a Washington Post-ABC News poll.

The survey found that six in 10 Americans favored a nuclear response if Hussein orders use of chemical or biological weapons on U.S. troops. Slightly more than a third -- 37 percent -- were opposed.

Nearly nine in 10 Americans said the United States is headed for war with Iraq, which most Americans believe possesses weapons of mass destruction.

"We need to get Saddam Hussein out of power, even if it means using nuclear weapons, particularly if they attack us with dirty weapons," says Rebecca Wingo, 35, a trucking dispatcher who lives in Johnstown, Ohio. "When you're dealing with people like him, the only thing they understand is brute force."

But the new survey also found that 58 percent of those interviewed would like to see President Bush present more evidence explaining why the United States should use military force to topple the Iraqi leader, up from 50 percent in September. And while most Americans view Iraq as a major threat, fewer than half said it poses an immediate danger to this country.

That finding and others suggest that Bush may be moving faster toward war than the public would prefer. At the time Americans are becoming more certain that war will break out, the survey found they also are growing more wary of the president and his motives for pressing to move quickly with military force against Iraq.

More than half -- 54 percent -- feared that Bush will act too quickly to use force, while 40 percent worried that he won't move quickly enough. And an even larger majority -- 58 percent -- opposed taking military action against Iraq without the support of the United Nations.

"Eventually, yes, I believe we will have to use force," says David Sherman, 49, who delivers medical oxygen and lives outside Grand Rapids, Mich. "But . . . I have not seen enough that would make me give my support for sending troops to go in right now."

Nina Russell, 67, of Mettie, W.Va., says, "It's really looking like war, but I'd like to know more facts about what Iraq has and what our friends plan to do. I worry that Bush has made it personal with Saddam Hussein."

For some Americans, skepticism about Bush's motives makes it even more important that the United States secure support from its allies.

"He's got that little smirk on his face," says Brian Rust, 51, a Realtor living in Moneta, Va. "After 9/11, he wants to go out after some of those countries that were behind this and behind that. It concerns me a little bit. That's why I think it's important to have support from other countries, to use their airstrips or at least be able to say we have their support."

Overall, six in 10 -- 62 percent -- said they support using U.S. forces to topple Hussein. But when asked specifically if the United States should send American ground troops to invade Iraq, fewer than half -- 45 percent -- said yes while 50 percent disagreed.

Two-thirds of those interviewed said Bush has done enough to win the backing of other countries, up from barely half three months ago. Among those who say Bush has done enough, seven in 10 favored military strikes against Iraq. But among those who say he needs to do more, 54 percent opposed the military option, a finding that underscores the importance for Bush to secure international backing.

Overall, six in 10 -- 62 percent -- said they support using U.S. forces to topple Hussein. But support for a U.S. invasion of Iraq with ground forces stands at only 45 percent with 50 percent opposed.

A total of 1,209 randomly selected adults were interviewed Dec. 12-15 for this survey. The margin of sampling error for the overall results is plus or minus 3 percentage points.

The poll found that homeland security, the war on terrorism and Iraq dominate the public's agenda, and overwhelm such perennial concerns as education, health care and Social Security. Nearly half of the country said homeland security and the campaign against terrorism were issues they wanted Bush and the Congress to give their "highest" priority. Four in 10 rated the economy and Iraq as a priority.

"After September 11, I'm feeling a little less secure," says Shannon Groskreutz, 22, a recent college graduate in Tallahassee. "I know the world is changing, and we need to concentrate right on making our country safer as well as spreading peace before we go on to other issues."

Barely six weeks after

Republicans claimed both chambers of Congress in the midterm elections, this mix of defense and security issues has given Bush and the GOP a clear advantage over Democrats. By 2 to 1, the public trusts the Republicans more than Democrats to handle homeland security, terrorism and the situation with Iraq. The two parties are at parity on handling the economy, which barely a third of the public rated as "excellent" or "good."

Democrats hold more modest advantages over the GOP on domestic issues such as health care, education, Social Security and prescription drugs, issues that only a third or fewer Americans now rate as top priorities for Bush and Congress.

The Republican Party, by 44 to 41 percent, continues to be viewed by the public as the party best able to deal with the country's biggest problems.

Bush's overall job approval rating stood at 66 percent. Even larger percentages of Americans said they approved of the way the president is handling the anti-terrorism campaign (79 percent), while two-thirds approved of the way he is dealing with homeland security concerns. Nearly six in 10 -- 58 percent -- approved of the way he is handling the confrontation with Iraq.

Claudia Deane, The Washington Post's assistant director of polling, contributed to this report.