The U.S. military issued a sober assessment Tuesday of the Baghdad security crackdown, saying violence had decreased slightly but not to "the degree we would like to see" in the two weeks since 75,000 Iraqi and American troops flooded the capital.

The evaluation came as 18 more Iraqis fell victim to sectarian and insurgent violence, including five people whose bodies were found dumped in Baghdad. The U.S. military also announced the deaths of a Marine and three soldiers; three of the deaths were west of the capital in volatile Anbar province, an insurgent stronghold.

Maj. Gen. William Caldwell, spokesman for U.S. forces in Iraq, said the overwhelming security operation launched two weeks ago to rein in violence in Baghdad was moving more slowly than hoped.

CountryWatch: Iraq

"It's going to take some time. We do not see an upward trend. We ... see a slight decrease but not of the degree we would like to see at this point," he said at a news conference in the heavily fortified Green Zone.

However, Caldwell added, "we don't see this as turning into a civil war right now."

U.S. officials hope the willingness of leading Sunni Arabs to withdraw support for the insurgency will help heal the nation.

On Tuesday, an influential Sunni Arab cleric endorsed the Shiite Prime Minister Nouri al-Maliki's 24-point reconciliation plan.

Ahmed Abdul Ghafour al-Samaraie, the head of the Sunni Endowment, the state agency responsible for Sunni mosques and shrines, applauded the provision that calls for the release of all prisoners who have not been charged with crimes.

He called on the government to implement the plan quickly, but emphasized that it should include the disbanding of armed Shiite militias. Minority Sunnis have accused Shiite-led militias — who have infiltrated the police and armed forces — of random detention, torture and killing.

"We bless this initiative," al-Samaraie said. "We see a glimmer of hope in this plan, but at the same time we are noticing that some people are pushing the armed groups to attack some areas in Baghdad, spreading terror and chaos in the city in order to make this plan a failure. ... The government will not be able to enforce the law while those militiamen consider themselves above the law."

Al-Maliki's plan is vague on this issue, saying only that the government should address the "problem of sectarian militias and illegal armed groups through political, economic and security measures." Al-Samaraie urged the government to provide more details about the plan, which parliament will debate.

Al-Samaraie's endorsement came a day after key lawmakers said seven Sunni Arab insurgent groups offered the government a conditional truce. The seven groups do not include al-Qaida or Islamic terror groups. They are mostly made up of former members or backers of Saddam Hussein's government, military or security agencies.

On Tuesday, Deputy Prime Minister Salam Zikam Ali al-Zubaie said he had met secretly in Jordan with exiled Sunni tribal leaders from Anbar province to win their support for al-Maliki's plan. Al-Zubaie said the meeting took place before al-Maliki unveiled the plan Sunday.

"We have reached positive results so that they can try to persuade members of the honorable resistance to join the political process," al-Zubaie told The Associated Press in a telephone interview. Many Iraqis refer to those who have attacked only foreign troops in Iraq as the "honorable resistance" because they do not target Iraqis.

"There is no dialogue with those who targeted Iraqis," said al-Zubaie, a member of the influential Sunni Arab Zubaa tribe.

He said the tribal leaders called for the release of detainees, an end to military operations in Sunni areas and a halt to detentions.

The Justice Ministry, meanwhile, said 453 more detainees were released from U.S. detention centers across Iraq, part of al-Maliki's plan to free 2,500 by the end of June as a goodwill gesture.

In the first tangible step after al-Maliki's reconciliation plan was announced, the Council of Ministers said it will reinstate the jobs of government employees who were detained and recently released. It said the government will consider their service uninterrupted when considering bonuses, promotions and retirement privileges.

The ministers said they will allow freed students to return to school and take final exams, and that their absence in the 2005-2006 academic year will not be held against them.

Separately, the Iraqi High Tribunal announced that Saddam Hussein and six members of his former regime will be put on trial Aug. 21 for a 1980s campaign that killed an estimated 100,000 Kurds and saw thousands of their villages razed. The trial will be the second for Saddam and top officials of his Baath Party regime. More trials over crimes committed during his 23-year dictatorship are also expected.

An American soldier on a foot patrol south of Baghdad was killed Tuesday in a bombing, and a Marine died Tuesday in fighting in Anbar province west of the capital. The military also announced the deaths of two soldiers killed Monday in Anbar fighting.

In other developments:

• A suicide car bomb struck a busy gas station in the northern city of Kirkuk, killing at least three people and wounding 17.

• A parked car packed with explosives blew up at an open-air market in a Shiite section of Baghdad's predominantly Sunni Dora neighborhood, killing three people and wounding 10, police said.

• A university professor was killed in a drive-by shooting in Baghdad's upscale Mansour neighborhood. The Ministry of Higher Education and Scientific Studies said it will stage a sit-in at all universities Wednesday to protest kidnappings and violence against its employees.

• Gunmen ambushed a convoy carrying a tribal leader in Dujail, north of Baghdad, killing him and four drivers.

• A tribal chief in the southeastern town of Amarah was seriously wounded in an assassination attempt. Sheik Kadim al-Sebahawi's 22-year-old son died in the attack.