Baghdad, Iraq ? On the last day of campaigning, a roadside bomb killed four American soldiers Tuesday, and gunmen assassinated a candidate for parliament in this week’s election. A Shiite politician escaped injury in a bombing south of Baghdad.

The U.S. ambassador, meanwhile, said Tuesday the total number of abused prisoners found so far in jails run by the Shiite-led Interior Ministry came to about 120. The statement by Ambassador Zalmay Khalilzad reinforced Sunni Arab claims of mistreatment by security forces – a major issue among Sunnis in the election campaign.

Despite the violence, more than 1,000 Sunni clerics issued a religious decree instructing their followers to vote Thursday, boosting American hopes the election will encourage more members of the disaffected minority to abandon the insurgency.

Three of Iraq’s leading politicians agreed Tuesday that a speedy withdrawal by foreign troops before Iraqi forces are ready would cause chaos.

But the three – former Prime Minister Ayad Allawi, Kurdish leader Massoud Barzani and Sunni Arab politician Tariq al-Hashimi – disagreed on the description of U.S. and other foreign troops. Barzani described them as “forces of liberation,” while al-Hashimi said they were occupiers.

The three leaders, speaking from Baghdad, appeared in a debate on the Dubai-based Al-Arabiya television. Such debates are rare in the Arab world, where candidates mainly rely on rallies attended by hand-picked followers.

Their comments were noteworthy because they represent important constituencies in the Thursday vote, when Iraqis will choose a 275-member parliament to serve for the next four years.

Barzani heads the Kurdish autonomous region in the north and is among the country’s most powerful politicians. Allawi heads a religiously mixed ticket in the Thursday election. Al-Hashimi represents a major Sunni Arab coalition and is a candidate for parliament.

Allawi, a secular Shiite, said an early U.S. withdrawal “will lead to a catastrophic war.” And al-Hashimi, whose party has been sharply critical of the U.S. role, said he looked forward to “my country’s liberation” but not “to be followed by chaos.”

Al-Hashimi criticized President Bush for saying the United States is fighting terrorism in Iraq.

“Why should Iraqis pay a bill for something they have nothing to do with?” he asked. “Terrorism is not the problem of Iraqis.”

A U.S. military statement said four soldiers from Task Force Baghdad died in a blast northwest of the capital, but did not specify the location. That brought to at least 2,149 the number of U.S. service members to have died since the start of the war in 2003, according to an Associated Press count.

Elsewhere, gunmen killed Sunni Arab candidate Mezher al-Dulaimi as he was filling his car at a gas station in Ramadi, an insurgent stronghold 70 miles west of Baghdad. Al-Dulaimi took part in a conference last month in Cairo that was attended by representatives of Iraq’s major factions.

A prominent Shiite politician, Jalal Eddin al-Sagheer, escaped injury Tuesday when a bomb exploded near his convoy in Latifiyah, about 20 miles south of Baghdad.

The attacks occurred on the second anniversary of the capture of Saddam Hussein, an event hailed at the time as a turning point in an insurgency, which actually grew in wake of the arrest.

The Bush administration hopes the election will draw a large turnout among Sunni Arabs and produce a government that can win the trust of the community that is the backbone of the insurgency.

That would in turn allow the United States and its coalition partners to begin bringing their troops home next year.