BAGHDAD, Iraq - A roadside bomb exploded today near a passing convoy of American security guards in the southern city of Basra, killing four contractors, a U.S. Embassy spokesman said.

Three of the men were killed instantly and a fourth died after British troops took him to a military hospital, embassy spokesman Peter Mitchell said.

"All four individuals worked for a private security firm supporting the regional U.S. Embassy office in Basra," Mitchell said in a statement.

Meanwhile, Iraq's president said Saddam Hussein has confessed to ordering killings and other crimes committed during his regime, including the massacre of thousands of Kurds in the late 1980s. Jalal Talabani said the deposed leader should be executed many times over.

In Baghdad, gunmen shot and killed a top Iraqi Defense Ministry official today as he drove through a dangerous neighborhood in the south of the capital. Separately, insurgents attacked an Interior Ministry commando patrol in the west of the city, killing a colonel and wounding four bodyguards.

Also today, Baha al-Araji, deputy head of the Constitution Committee, said the new charter would be sent to the government printing house Thursday. He said it stood unchanged from the version sent to parliament by the drafting committee Aug. 28 after several deadlines were missed.

Talabani, a Kurd, said the version to be printed did contain one revision, a bow to an Arab League demand that the constitution acknowledge the country's role as a founder of the pan-Arab group. Before that revision, the document said Iraq was an Islamic country but omitted references to its history as a key player in the Arab world.

Vice President Ghazi Al-Yawar, a Sunni, said the new constitution did not meet the minority sect's demands "100 percent," but encouraged its adoption. The task now, he said, was for Sunnis to engage in upcoming parliamentary elections to boost their representation in the legislature for a future bid to amend the charter.

The leaders spoke at a memorial for victims of the Aug. 31 bridge stampede in which more than 900 people died attempting to reach a Shiite mosque in northern Baghdad during a holy day pilgrimage.

Iraqis will vote on the charter in an Oct. 15 referendum, with the outcome still not assured because of fundamental opposition from the country's Sunni minority, which governed under Saddam. Five million copies of the constitution are to be distributed around the country with monthly food rations.

On Tuesday evening, Talabani told Iraqi television that an investigating judge "was able to extract confessions from Saddam's mouth" about numerous executions he had allegedly personally ordered during his 24 years in power.

But a legal consultant retained by Saddam's family expressed skepticism over the claim, saying the former strongman had not mentioned any confession when he met his lawyer on Monday.

Saddam's trial is scheduled to open on Oct. 19. He and seven other senior Baath Party officials have been charged for their alleged role in the 1982 massacre of Shiites in Dujail, a town north of Baghdad, following an assassination attempt there against him.