President Bush's national security adviser said Sunday that Iraqi leaders had "stared into the abyss" and determined that sectarian violence was not in their interest.

Although bombings and other attacks have surged in the last week, Stephen Hadley expressed optimism in the light of statements from Iraqis who have condemned the attacks and pledged to move forward with building a unity government.

"It is a time of testing for Iraqis," Hadley said on CBS' "Face the Nation."

"They've stared into the abyss a bit, and I think they've all concluded that further violence, further tension between the communities, is not in their interest," he said.

Hadley said the hope is that advancing the political agenda and continuing to train Iraqi security forces will work against the terrorist attacks.

"There has to be the country coming together and committing to a unified future together. That is the process we hope will be accelerated by this. That is the hope out of this tragedy," he said.

Sen. Carl Levin of Michigan, the senior Democrat on the Senate Armed Services Committee, said Iraq's political leaders should be pressured to form their unity government in the next six weeks to eight weeks.

If that doesn't happen, Levin said, the U.S. should reassess its presence.

"There's no point in our staying if they don't get their political house in order, because without them coming together politically, there is no chance of them solving the insurgency problem," Levin said on "This Week" on ABC. "That's our military people telling us that."

Sen. Dianne Feinstein, D-Calif., said more sectarian violence and a failure to form a government would bring the country "a step away from major civil war."

"The worst thing would be for the United States to get caught in the middle," Feinstein told CNN's "Late Edition."

Feinstein criticized Bush for not stating his plan for dealing with a civil war if one were to develop.

"This is a deteriorating situation, and we have to deal with it as such and not just say, 'I'm optimistic,"' she said.

Sen. Kay Bailey Hutchison, R-Texas, said failure in Iraq could cause instability elsewhere in the Middle East. She said Bush was right not to take sides in Iraq's internal conflicts.