BAGHDAD, Iraq - Bomb blasts killed six Marines in western Iraq, and U.S. forces killed 29 militants in U.S. offensives aimed at uprooting al-Qaida insurgents ahead of the country's vote on a new constitution, the military said today.

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. They accused them of carrying out recent attacks on British and U.S. troops, officials said today, 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 across the country were still waiting to get copies of the document to pass out to voters. Some in Baghdad refused to have anything to do with the document, 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 who handed out about 150 copies today.

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

The Pentagon said today the military in Iraq had intercepted a letter from the second in command of al-Qaida, 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-Qaida 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. 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, 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.

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.“