Bomb blasts killed six Marines in western Iraq, and U.S. forces killed 29 militants in U.S. offensives aimed at uprooting Al Qaeda (search) insurgents ahead of the country's vote on a new constitution, the military said Friday.

The American deaths brought to 1,950 the number of U.S. troops who have died since the beginning of the war in 2003, according to an Associated Press count.

In southern Iraq, British troops detained 12 militiamen loyal to a radical Shiite cleric in the city of Basra (search), accusing them of carrying out recent attacks on British and U.S. troops, officials said Friday, amid charges Iran is helping fighters carry out deadlier bombings.

Eight days before Iraqis were to go to the polls to approve or reject the new constitution, officials were still waiting to get copies of the document to pass out to voters. Distribution began in a few Baghdad neighborhoods, but did not appear to have begun elsewhere.

Some shopkeepers in Baghdad refused to hand out the document and some people refused to take it, fearing reprisals by militants determined to wreck the crucial Oct. 15 referendum.

"Some people are excited to take it. Others are refusing to touch it," said Mohammed Ali, a shopkeeper in the western Baghdad neighborhood of Saydiya (search) who handed out about 150 copies Friday.

"I know some merchants who have refused to accept copies for distribution because they fear retaliation by the insurgents," Ali said in an interview at his shop.

Al Qaeda in Iraq and other Sunni-led insurgent groups have launched a wave of violence in the past two weeks that has killed more than 290 people, many of them Shiites. Al Qaeda in Iraq leader Abu Musab al-Zarqawi has declared war on Iraq's Shiite Muslim majority.

The Pentagon said Friday the military in Iraq had intercepted a letter from the second in command of Al Qaeda, Ayman al-Zawahri, to al-Zarqawi, urging him to avoid bombing mosques and slaughtering hostages to avoid alienating the masses.

Pentagon spokesman Bryan Whitman said the letter also demonstrates "detailed planning and intent on the part of the insurgents in Iraq to one day control that country and to really try to extend their extremism to neighboring countries."

The U.S. military is waging two large offensives in western Iraq — operations "Iron Fist" and "River Gate" — to oust Al Qaeda in Iraqi militants from a half-dozen towns along the Euphrates River valley.

Two Marines were killed Thursday by a roadside bomb that hit their patrol outside the town of Qaim, the region near the Syrian border where Iron Fist is being waged, the military said.

Their deaths bring to six the number of U.S. troops killed in Iron Fist and River Gate, launched Oct. 1 and Tuesday, respectively.

Apart from the offensives, four Marines were killed Thursday by a roadside bomb in Karmah, near the town of Fallujah, 40 miles west of Baghdad, the military said.

On Thursday, warplanes dropped four precision-guided bombs on an abandoned three-story hotel seized by militants in the town of Karabilah, near the Syrian border, the focus of the Iron Fist assault. Twenty militants were killed in the bombardment, the military said. Seven more insurgents were killed when planes destroyed three buildings from which gunmen were firing on Marines, and two gunmen were killed in fighting in Karabilah.

The 29 deaths raised the insurgent death toll in Iron Fist to 71. At least six insurgents have been reported killed in River Gate offensive.

In Syria, President Bashar Assad was quoted Friday as saying that his country wants to close its border with Iraq to Islamic militants but U.S. troops were doing nothing on the other side to stop the flow of fighters.

"They have no patrols at the border, not a single American or Iraqi on their side of the border," Assad told the pan-Arab newspaper Al Hayat. "We cannot control the border from one side."

Assad also said the U.S. forces in Iraq want Syria's help in "getting out of the political predicament they're in."

"But their blunders are so huge I cannot imagine that Syria, or anyone else, could help them," Assad said in the interview.

The British raid in Basra targeted a house and netted 12 members of the al-Mahdi militia, the armed force loyal to radical Shiite cleric Muqtada al-Sadr, said British military spokesman Maj. Steven Melbourne. Britain's Ministry of Defense confirmed the raid.

On Thursday, British Prime Minister Tony Blair said his government suspects that Iran and Lebanon's Hezbollah might be supplying technology and explosives to Shiite Muslim militant groups operating in Iraq, but he provided no proof.

Sheik Khalil Al-Maliki, a member of the al-Mahdi militia, told the AP that British soldiers and tanks raided the home of police officer Ali Eliwi late just after midnight in the early hours Friday, detaining Eliwi and 11 other Iraqis there and seizing their weapons.

"I think the reason is the recent British claim about Iranian interference in Iraqi affairs," Al-Maliki said.

British and U.S. forces have been attacked in recent months by roadside bombs packed with "shaped charges," which are much more deadly than conventional roadside bombs.

Such attacks have killed six British troops since July. Late last month two U.S. soldiers were killed when a bomb exploded near their vehicle in Shaibah, a town near Basra.

Iran rejected Blair's accusations as "baseless," saying it "has no motive for intervening in the domestic affairs of Iraq." Foreign Ministry spokesman Hamid Reza Asefi said in a statement read on state television Friday that "Blair is accusing others to cover up Britain's failure to provide security in Iraq."

In Beirut, Hezbollah denounced Blair's accusations as "lies."

The arrests in Basra on Thursday night could increase tensions between the 8,500 British troops in Iraq and the provincial government and people of Basra, Iraq's second-largest city.

Last month, British forces used armored vehicles to storm a Basra jail and free two of their soldiers who had been arrested by police. During the raid, British forces learned that Shiite Muslim militiamen and police had moved the men to a nearby house. The British then stormed that house and rescued them.

At least five Iraqi civilians were reported killed in the fighting, and Basra's provincial government responded by suspending all cooperation with British forces. It also demanded the return of the two British soldiers, but Britain's government has refused.

In new violence in Baghdad, at least seven Iraqi civilians were killed in shootings around the city, and at least two bodies were found dumped in the capital.

Sunni Arabs held a funeral for 22 Sunnis who were abducted in Baghdad nearly two months ago and whose bound and bullet-ridden bodies were found a week ago near the Iranian border. The mourners accused government-allied militiamen of killing them.