A congressional delegation visiting Baghdad told Iraqi leaders "in no uncertain terms" that they must take on more of a leadership role to end the country's continuing sectarian violence, Sen. John Thune, R-S.D., said Wednesday.

Thune, speaking with The Associated Press by telephone, said Americans' support for the military's efforts is predicated on the Iraqis stepping up to address their country's political conditions. The U.S. lawmakers delivered the message to Prime Minister Nouri al-Maliki and U.S. generals that they need to come up with a plan to stop Sunni Arabs and Shiites from killing each other so the country can be secured, Thune said.

"And we delivered it in no uncertain terms," he said. "We really hammered that home."

Thune is visiting the region as part of a delegation that includes Sens. John McCain, R-Ariz.; Joseph Lieberman, D-Conn.; Lindsey Graham, R-S.C.; Susan Collins, R-Me.; and Rep. Mark Kirk, R-Ill.

Many in the delegation have taken issue with parts of the Iraq Study Group's report that recommends major changes in the U.S. handling of the Iraq war.

Maj. Gen. William Caldwell, the top American military spokesman in Iraq, said Wednesday that violence had reached unacceptable levels in Baghdad, which has been hit by several car bombs in recent days. On Wednesday, a car bomb exploded near a crowded bus stop in eastern Baghdad during morning rush hour, killing 11 people and wounding 27 in a mostly Shiite area, according to police.

Thune said he had a chance to meet with some Baghdad residents to get their take on the situation.

"People are scared, just as you'd expect them to be, as they go about their daily business," he said. "But they are appreciative of the U.S. presence here, because I think they realize without it, it would dissolve into chaos and anarchy and probably make conditions a whole lot worse."

The Iraq Study Group this month concluded that the U.S. could be out of Iraq by early 2008 if it dramatically increased the number of troops advising Iraqi units and threatened to cut off aid to the Iraqi government unless it met certain milestones. The bipartisan panel also suggested asking Iran and Syria to pressure militias inside Iraq to stop sectarian killings.

Thune said those he talked to in Baghdad disagree with the study group's dire characterization of the country.

"The Iraq Study Group described the conditions here as grave and deteriorating and nobody here buys that assessment," Thune said. "They think that's overstating it, but they also say this sectarian violence has really become a problem and is going to have to be addressed."

Iraq President Jalal Talabani has denounced the report, saying it offered dangerous recommendations that would undermine his country's sovereignty and were "an insult to the people of Iraq."

Thune said many in Baghdad are upset with the panel's calls to reduce the number of U.S. troops. But he said Iraqi leaders acknowledge the importance of some of the report's other recommendations, such as Iraq assuming more responsibility for its security and building a police force that's independent and not in cahoots with the armed militias.

"The Iraq Study Group's findings and recommendations certainly met with mixed reviews here," Thune said. "But in the end, I think that the leaders here also recognize where they have to go. What we're trying to do is get them there faster."

Lieberman and Collins have both said they are skeptical about approaching Iran to get help stabilizing Iraq.

Also, McCain has questioned the wisdom of the recommendation that many more U.S. troops be placed inside Iraqi combat units to advise and train them on the battlefield. He said this was too dangerous.

During a conference call with South Dakota reporters on Wednesday, Sen. Tim Johnson, D-S.D., said "there's a lot that's very worthwhile" in the panel's report. He said he agrees the United States needs to transfer more responsibility to Iraqis.

"We need to create an environment where we can get our troops home, or at least get them out of harm's way," he said

"Clearly we have done a great deal for the Iraqi people, but we cannot have an indefinite stay in Iraq," Johnson added.

Thune said Iraqis have to take steps to defend themselves so the U.S. can start reducing its troop levels.

"There's an appreciation for the U.S. role here," Thune said. "There's also a recognition that it can't last forever."