A U.S. Congressional delegation is in Iraq to meet with the country's interim government leaders and U.S. military commanders. Amid continuing violence, the senators say Iraq still needs U.S. and coalition support, and vowed to see the job through.

The five-member delegation's first day in Iraq was marked by a series of attacks and bombings, which occurred as Shiite Muslims celebrated Ashura - the holiest day of the Shiite religious calendar.

Despite the deadly violence, Senator Hillary Clinton, a Democrat from New York, said she was cautiously optimistic about Iraq's future.

"Cautious because there are so many challenges ahead," she said. "Cautious because there are neighbors of Iraq that are not necessarily enthusiastic about the success of the Iraqi people in creating and sustaining a multi-ethnic, multi-religious democracy. But optimistic, because the results of the election are a strong rebuke to those who didn't believe the Iraqi people would take this opportunity to demonstrate their commitment to their own future."

The delegation spent the day in meetings with Iraq's interim prime minister, and other government officials. They also met with U.S. Lieutenant General David Petraeus, who is heading the effort to create an independent Iraqi security force.

Senator Lindsey Graham, a Republican from South Carolina, said U.S. troops would remain in Iraq until the job is done.

"Not one minute longer, not one minute less," he said. "And what is the job? The ability of this country to have the capacity to maintain its freedom. That just doesn't mean numbers [of people] with guns, it means institutions that work."

Due to the security situation, the delegation did not leave the heavily guarded "Green Zone," home to Iraqi government institutions and the U.S. and British Embassies.

Susan Collins, a Republican from Maine, said, while Baghdad was clearly more fortified than it was when she last visited in the summer of 2003, she believed the recent elections were an important step.

"Although it's disappointing to see that the violence that has ensued since my last visit has resulted in an Iraq where it is more difficult to move around, there's no doubt in my mind that the long-term future of the Iraqi people is far brighter and that the transition to power in the hands of the Iraqi people has and is occurring," she said.

On Sunday, the delegation will travel to U.S. bases elsewhere in Iraq to meet with American soldiers and Marines.