RENO, Nev. — President Bush told a receptive audience of veterans on Tuesday that an American withdrawal from Iraq would unsettle the entire Middle East, create a haven for al-Qaida and embolden a belligerent Iran.
Fighting in Iraq on Tuesday claimed 51 lives during a religious festival, forcing officials to halt the celebrations.
Bush said Tehran's nuclear programs threatened to put "a region already known for instability and violence under the shadow of a nuclear holocaust."
Speaking here before the American Legion's annual convention, Bush said that competing brands of Islamic extremism — the Sunni model exemplified by al-Qaida and a Shiite version that he said was abetted by Iran — were vying for dominance in Iraq. That, he said, made it imperative for the United States not to fail in establishing a pro-American government there.
"I want our citizens to consider what would happen if these forces of radicalism are allowed to drive us out of the Middle East," he said in a speech interrupted several times by applause. "The region would be dramatically transformed in a way that would imperil the civilized world."
Bush has previously warned Iran about its involvement in Iraq and its nuclear programs, but his remarks on Tuesday were especially forceful and suggested that he was blending the justification for staying in Iraq with fears held by members of both parties in Congress that Iran could emerge as a threat.
Fighting erupted Tuesday between rival Shiite militias in Karbala, Iraq, during a religious festival, claiming 51 lives and forcing officials to abort the celebrations and order up to 1 million Shiite pilgrims to leave the southern city.
Security officials said Mahdi Army gunmen loyal to radical cleric Muqtada al-Sadr fired on guards around two shrines protected by the Badr Brigade, the armed wing of the Supreme Islamic Iraqi Council.
Residents of Karbala contacted by telephone said snipers were firing on Iraqi security forces from rooftops. Explosions and the rattle of automatic weapons fire could be heard during telephone calls to reporters in the city 50 miles south of Baghdad.
In addition to the deaths, security officials said at least 247 people were wounded, including women and children.
At Reno, Bush reiterated accusations by officials and American military commanders that Iran was providing training and weaponry, including 240-mm rockets, to forces not only in Iraq, but also in Afghanistan, Lebanon and the Palestinian territories. He said he had authorized the military to "confront Tehran's murderous activities."
"For all those who ask whether the fight is worth it, imagine an Iraq where militia groups backed by Iran control larger parts of the country," he said.
One problem for Bush is that the most recent National Intelligence Estimate, an assessment released last week, suggested that that is already happening because of the uncertain motives of the Iraqi leaders Bush supports.
The future of Iraq has dominated Bush's recent public events, even as his administration dealt with the fallout of Attorney General Alberto R. Gonzales' resignation over the weekend. It has been a concerted effort to make his case before a new legislative fight once Congress receives a much-anticipated progress report from the administration and the military next month.
Although Democrats and even a few Republicans have urged the White House to rethink its approach, Bush, in his remarks, showed little sign of bending. Administration and military officials have already indicated that any reduction of troops from today's level, which exceeds 160,000, would be gradual and incremental, not the dramatic reductions that opponents have called for.
Congressional Democrats reacted with scorn to Bush's speech. "The president continues to suffer from the Katrina complex," Sen. Joseph R. Biden Jr. of Delaware told reporters during a conference call after the speech. "That's when you ignore all the warnings, bad things happen, you continue to follow the same bad policy, and things get worse."
Sen. Harry Reid of Nevada, the majority leader, said that Democrats will press their Republican counterparts again in the coming weeks for a change in American strategy in Iraq. "The president continues to stubbornly pursue a flawed strategy that has mired our troops in a civil war in Iraq and diverted our attention as Osama bin Laden and al-Qaida grow stronger," Reid said in a statement. "Most Americans, and a bipartisan majority in Congress, believe this strategy is not in our national interest and the time for a major change is now."
Last week Bush appeared before another veterans group, the Veterans of Foreign Wars in Kansas City, Mo., and recalled the anger, humiliation and turmoil that followed the American withdrawal from Vietnam. On Tuesday, he sought to raise the specter of a new haven for terrorists and an Iran that dominated the region, threatening allies and energy supplies.
"This scenario would be a disaster for the people of the Middle East, a danger to our friends and allies, and a direct threat to American peace and security," he said.
Bush did not directly rebut critics of the war, especially Democrats in Congress, but he sought to preempt the coming debate over the success of the troop buildup. He said that the greater military effort this year had increased security and yet was less than three months old.
He also noted rare progress on political issues, welcoming an agreement by Iraq's political leaders to make some modest steps toward the benchmarks outlined by Congress to evaluate Bush's military increase this year. And he urged patience. "It makes no sense to respond to military progress by claiming that we have failed because Iraq's Parliament has yet to pass every law it said it would," he said.
Contributing: Associated Press