BAGHDAD, Iraq -- The issue of U.S. troop levels echoed from Baghdad to Washington on Thursday, with Sen. John McCain calling for the deployment of 15,000 to 30,000 more troops to Iraq, and the Army's top general warning that his force "will break" without thousands more active-duty soldiers and greater use of the reserves.

McCain, who was visiting Baghdad with five other senators, said he realizes that few Americans favor deploying more U.S. troops to Iraq, and that if such a move proved unsuccessful in the unpopular war it could hurt his presidential ambitions. But he said if U.S. troops leave Iraq in chaos, groups such as al-Qaida "will follow us home and that we will have a large conflict and greater challenges than those that we now face here in Iraq."

"The American people are confused, they're frustrated, they're disappointed by the Iraq war, but they also want us to succeed if there's any way to do that," the Arizona Republican told reporters in Baghdad.

McCain's position puts him at odds with the bipartisan Iraq Study Group, which recommended withdrawing a substantial number of U.S. troops from the Iraqi civil war over the coming year. The Army in recent days has been looking at how many additional troops could be sent to Iraq if President Bush decides a surge in forces would be helpful.

Army officials say only about 10,000 to 15,000 more troops could be sent and an end to the war would have to be in sight because the deployment would drain the pool of available soldiers for combat. Currently, the U.S. military has about 140,000 troops in Iraq.

Further, many experts warn, there is no guarantee a surge in troops would work to settle the violence. "We would not surge without a purpose," the Army's top general, Peter Schoomaker, told reporters Thursday in Washington. "And that purpose should be measurable."

Noting the strain put on the force by operations in Iraq, Afghanistan and elsewhere in the global war on terrorism, Schoomaker said he wants to grow his half-million-member Army beyond the 30,000 troops already added in recent years. Although he didn't give an exact number, he said it would take significant time and commitment by the nation, noting some 6,000 to 7,000 soldiers could be added per year.

Officials also need greater authority to tap into the National Guard and Reserve, long ago set up as a strategic reserve but now needed as an integral part of the nation's deployed forces, Schoomaker told a commission studying possible changes in those two forces.

"Over the last five years, the sustained strategic demand ... is placing a strain on the Army's all-volunteer force," Schoomaker told the commission in a Capitol Hill hearing. "At this pace ... we will break the active component" unless reserves can be called up more to help, Schoomaker said in prepared remarks.

Speaking to reporters afterward, Schoomaker said Gen. George Casey, the top commander in Iraq, is looking at several military options for the war, including shifting many troops from combat missions to training Iraqi units. However, Schoomaker said, the military is more interested in getting the Iraqi security forces up to speed than anything.

McCain said conditions in some areas of Iraq have improved since his last visit in March, but "I believe there is still a compelling reason to have an increase in troops here in Baghdad and in Anbar province in order to bring the sectarian violence under control" and to "allow the political process to proceed."

Two other senators in the delegation, Joseph Lieberman, D-Conn., and Lindsey Graham, R-S.C., agreed. "We need more, not less, U.S. troops here," Lieberman said.

Another senator in the group, moderate Republican Susan Collins of Maine, was more cautious.

"Iraq is in crisis. The rising sectarian violence threatens the very existence of Iraq as a nation," she said. The current U.S. strategy in Iraq has failed, but "I'm not yet convinced that additional troops will pave the way to a peaceful Iraq in a lasting sense," Collins said.

"My fear is that if we have more troops sent to Iraq that we will just see more injuries and deaths, that we might have a short-term impact, but without a long-term political settlement," she said.

Collins' remarks appeared to reflect the findings of the Iraq Study Group, which concluded that sustained increases in U.S. troops would not solve the fundamental problem and that violence would renew once those forces left the area.

While the senators were meeting with U.S. and Iraqi officials in Baghdad, Iraq's Sunni vice president, Tariq al-Hashemi, was in Washington, where he called on the Bush administration to set a timetable for withdrawal of U.S. troops. Al-Hashemi said the timetable should be "flexible" and depend on development of an Iraqi security force.

Al-Hashemi told the United States Institute of Peace, a U.S.-financed think tank, that currently "there is across-the-board chaos in my country."

Graham said he was shocked by the situation in Baghdad.

"The first time I came here with Sen. McCain, we went rug shopping," Graham said. "Yesterday, we moved around in a tank. It's one of the most dangerous places on the planet."

At least 74 more people were killed or found dead in Iraq on Thursday, including 65 bullet-riddled bodies bearing signs of torture. And gunmen in military uniforms kidnapped as many as 70 shopkeepers and bystanders from a commercial area in central Baghdad. At least 25 were later released.