U.S. forces along the Euphrates River attacked the insurgent stronghold of Haditha early Tuesday, capturing a militant with ties to Al Qaeda in Iraq (search) and killing four others, the military said.

The assault on Haditha (search) followed a recent offensive to retake Tal Afar (search), another northern town, which U.S. commanders said netted more than 400 suspected militants. The Iraqi military said its troops had detained 36 others, including a Yemeni citizen, just south of Tal Afar.

In southern Iraq, a roadside bomb exploded near a convoy of Iraqi security guards and foreign contract workers outside Basra, killing four people, police said. While one Iraqi official said the four dead were Americans, U.S. officials were unable to confirm the report.

President Jalal Talabani (search), meanwhile, said in Washington that Iraq will not set a timetable for the withdrawal of U.S. troops.

At a news conference with President Bush, Talabani said U.S. forces are still needed in Iraq, despite some calls in the United States to start bringing them home.

"We will set no timetable for withdrawal. A timetable will help the terrorists," Talabani said. He said he hopes that Iraqi security forces will be ready to take over responsibility for the country by the end of 2006.

Bush also renewed criticism of Syria, accusing Iraq's neighbor of not doing enough to control the flow of fighters across the border. He said he would speak with U.S. allies with the aim of getting Damascus to change its behavior.

"The Syrian leader must understand we take his lack of action seriously," he said. "The government is going to be more and more isolated."

The Bush administration's top envoy in Iraq, Zalmay Khalilzad, warned Monday that the U.S. is running out of patience with Damascus and refused to rule out a military strike against Syria or punishment through the United Nations.

Insurgents in Baghdad shelled the heavily fortified Green Zone, with two mortar rounds exploding near a military hospital inside the protected area that houses the Iraqi government, parliament and foreign missions, but there were no reports of casualties. Security inside the Green Zone was boosted earlier this month after reports that bombers were trying to penetrate the area.

Associated Press Television News video of the aftermath of the Haditha attack showed at least three demolished homes. There were no American casualties, the military said.

"Coalition Forces engaged the terrorists and called in close air support. Coalition aircraft destroyed one of the vehicles being used by one of the terrorists," the statement said.

Haditha, 140 miles northwest of Baghdad, is one of a series of towns in the Euphrates River valley controlled by militants.

On Monday, officials said the insurgent death toll in three days of fighting in Tal Afar totaled 200. Seven Iraqi soldiers and six civilians also died; the U.S. military said no American soldiers were hurt.

"Now, (the guerrillas) are just trying to save themselves by hiding in houses and communities," said Col. H.R. McMasters, commander of the American contingent from the 3rd Armored Cavalry Regiment. "The enemy no long enjoys any kind of a safe haven or a support base in the city."

"This operation was very precise. We've had access to all the terrorist safe havens," said Brig. General Muhsen Yahya, commander of the Iraqi Army's 1st Brigade in Tal Afar.

Prime Minister Ibrahim al-Jaafari flew to Tal Afar on Monday to congratulate his army, and Al-Iraqiya state television said he went despite insurgent threats "to attack the city with chemical and biological weapons."

There was no known public threat from the insurgents to use unconventional weapons in Tal Afar, but militants made two Internet postings in recent days vowing to stage chemical attacks on the Green Zone.

The Islamic Army in Iraq, which has previously claimed responsibility for kidnappings and killings of foreigners, made a bounty offer for the assassination of key Iraqi officials.

The militant group called in a Web posting for its "holy fighters to strike the infidels with an iron fist." It offered $100,000 to the killer of al-Jaafari, $50,000 for the interior minister and $30,000 for the defense minister.

Iraq's U.S.-trained forces and U.S.-backed government are waging their own media offensive, using the Tal Afar operation to position themselves as a confident and strong team leading the fight to wipe out insurgent forces.

"I met today with the commander of the 3rd Division in Tal Afar and his officers and soldiers and found them in high spirits," al-Jaafari said. Hundreds of Iraqis danced, sang and waved flags as the prime minister toured the region.

In the Basra bombing, APTN video showed a wrecked SUV at the side of the highway about 20 miles south of the city, near the town of Zubair. British soldiers and Iraqi police blocked off the area.

Capt. Mushtaq Kadim of the Basra Rapid Response Unit said the four dead were Americans. But U.S. diplomatic and military officials in Baghdad were unable to confirm the report, saying only that the victims were not diplomats or soldiers.

Although southern Iraq, where some 8,500 British troops are deployed, has been mostly calm since U.S. and British forces occupied Iraq more than two years ago, there has been increasing violence there in the past two months.

On Sept. 7, a roadside bomb exploded near a passing convoy of U.S. diplomatic security guards, killing four Americans.

In other developments Tuesday:

— Gunmen shot and killed two Sunni clerics in Baqouba, a town 35 miles northeast of Baghdad.

— Two truck drivers delivering concrete blast walls from a factory in Iraqi Kurdistan were ambushed and killed in Baghdad. The blast walls are used throughout Baghdad to secure government buildings, hotels, embassies and other potential targets from bombers.

— Police found the body of a former judge in Baghdad's eastern neighborhood of Sadr City. A note left next to it said: "This is the destiny of those who support Saddam."

— A bomb planted aboard a minibus exploded in Hilla, a town 60 miles south of Baghdad. Two civilians were killed and six injured, police said.

— In Samarra, north of Baghdad, U.S. soldiers killed two insurgents who were trying to plant a roadside bomb, the military said.