Iraq's president, an influential Sunni Muslim (search), threw his support Wednesday behind holding the Jan. 30 election on time despite insurgent threats he said have paralyzed voter registration voter registration in some Sunni areas of the country.

Moving to bolster security ahead of the vote, the United States said it was expanding its military force in Iraq by 12,000 to about 150,000 by year's end — the higest level of the war. The previous high was 148,000 on May 1, 2003, when President Bush declared that major combat operations were over.

Bombers targeted U.S. and Iraqi forces Wednesday on the road to Baghdad (search) airport and near a bridge south of the capital — grim reminders of the perilous security situation.

U.S. troops fought a half-hour gunbattle with insurgents in the northern city of Mosul (search), and one American was wounded. Clashes also occurred between U.S. troops and insurgents in Samarra, 60 miles north of the capital, wounding three Iraqi soldiers and two civilians, Iraqi officials said.

A militant group, meanwhile, claimed it had abducted and killed three Iraqis who worked for the U.S. Marines in Ramadi, saying in an Internet posting that Iraqis who cooperate with U.S. forces will face the same treatment as if they were Americans.

Iraq's interim Prime Minister Ayad Allawi (search) met Iraqi Sunni tribal leaders in Amman, Jordan, trying to drum up support for the election, which is seen as vital for building a democratic government in Iraq. Allawi ruled out meeting leaders of the insurgency but conferred with figures who are influential in Sunni regions of central Iraq where insurgent violence has been fiercest.

Insurgent attacks have raised concern that voting will be impossible in some areas of central and northern Iraq, and leading Sunni clerics have called for a boycott to protest the U.S.-Iraqi offensive on Fallujah and the continued American military presence.

That prompted several key Sunni Arab politicians to call for delaying the balloting by up to six months to buy time to resolve the security crisis and persuade Sunni clerics to drop their boycott call.

However, President Ghazi al-Yawer, who wields considerable influence among Sunni tribal figures, told reporters in Baghdad he opposed any delay.

"I personally think that there is a legal and a moral obligation to hold elections on the set date," he said. "Legally and morally, we have to abide by the date set for the elections in the country's administrative law" which mandates a ballot by the end of January.

Al-Yawer acknowledged security in some Sunni areas has disrupted preparations for the election, in which Iraqis will choose a national parliament to draft a permanent constitution.

"There are areas in Iraq where the security situation is very bad," he said. "There are areas where no one has been able to give out even one voter registration sheet."

In Mosul, an American military group touring the city to discuss election preparations came under rocket-propelled grenade and small arms fire Wednesday, according to witnesses.

One American soldier was wounded in the gunbattle that followed, the witnesses said. Mosul's 5,000-member police force disintegrated during an insurgent uprising last month, forcing the U.S. command and the interim government to divert troops from the offensive in Fallujah.

Elsewhere, three people were wounded Wednesday in a roadside bombing on Baghdad's airport road, one of the most dangerous routes in the country, Iraqi officials said. The explosion occurred at the same place where a bomber rammed a U.S. military convoy Tuesday, wounding several soldiers and destroying two Humvees.

A bomber blew up his vehicle Wednesday at an Iraqi checkpoint near the insurgent stronghold of Iskandariyah, 30 miles south of Baghdad, wounding seven Iraqis, the U.S. military reported.

Last week, U.S. Marines, British troops and Iraqi commandos launched an operation to clear guerrillas from towns and villages along the major highway linking Baghdad with Shiite cities to the south. The U.S. military said it has arrested 210 suspected militants in the weeklong crackdown.

In northern Iraq, gunmen opened fire on technicians sent out to repair the main northern oil pipeline in the Safrah area, 50 miles southwest of Kirkuk. One man was injured. The pipeline, which has been sabotaged repeatedly, carries crude oil to Turkey.

Three Iraqi National Guardsmen were wounded by a roadside bomb in Kirkuk Wednesday when insurgents ambushed them on their way to the Northern Oil Company's headquarters, Brig. Gen. Sarhad Qader said.