Updated

As 55 people died in Iraq on Saturday, the holiest day on the Shiite (search) Muslim religious calendar, Sen. Hillary Rodham Clinton (search) said that much of Iraq was "functioning quite well" and that the rash of suicide attacks was a sign that the insurgency was failing.

Clinton, a New York Democrat, said insurgents intent on destabilizing the country had failed to disrupt Iraq's landmark Jan. 30 elections.

"The concerted effort to disrupt the elections was an abject failure. Not one polling place was shut down or overrun," Clinton told reporters inside the U.S.-protected Green Zone, a sprawling complex of sandbagged buildings surrounded by blast walls and tanks. The zone is home to the Iraqi government and the U.S. Embassy.

The five-member U.S. congressional delegation arrived in Baghdad as a series of suicide bombings and explosions killed 55 people, including an American solder. Much of the violence was aimed at Shiite Muslims, commemorating Ashoura (search), the festival marking the 7th century death of a leader of their sect.

"The fact that you have these suicide bombers now, wreaking such hatred and violence while people pray, is to me, an indication of their failure," Clinton said.

The senate delegation included Republicans John McCain of Arizona, Susan Collins of Maine, Lindsey Graham of South Carolina and Wisconsin Democrat Russ Feingold.

All but Feingold are members of the Senate Armed Services Committee, which oversees the defense department budget.

Clinton said the last time she visited Iraq in late 2003, she traveled to the Green Zone by road from the international airport.

Today, security is so bad that none of the senators dared drive through Baghdad's streets, even in armored cars. Aside from the Green Zone (search), their only glimpse of the capital came from the relative safety of U.S. military helicopters that ferried them from the airport.

"It's regrettable that the security needs have increased so much. On the other hand, I think you can look at the country as a whole and see that there are many parts of Iraq that are functioning quite well," Clinton said.

Collins, who last visited Iraq in mid-2003, said the increased violence was "disappointing."

A year and-a-half ago, "we were able to move more freely in Baghdad," she said. "And one impression I have is how much more fortified Baghdad is than it was during that summer."

But Collins said much had been achieved since then, above all, the June handover of sovereignty from U.S. authorities to Iraq's interim government.

On Sunday, the senators will visit U.S. troops in other parts of Iraq.

McCain said his delegation met Saturday with interim Prime Minister Ayad Allawi (search), deputy Prime Minister Barham Saleh and Lt. Gen. David Petraeus, who is leading the American push to train Iraqi security forces so U.S. can eventually leave.

Clinton and McCain have often challenged the Pentagon's planning and its management of the Iraq war.

"I've said many times that we've made serious mistakes and we've paid a very heavy price for those mistakes," McCain said.

"We have a long, hard, difficult struggle ahead of us, but I'm far more optimistic than I was before the election, because the Iraqi people proved that they would brave the risk of their very lives in order to choose their government," he said. "To me, that's very encouraging."

Graham said the U.S. military was unlikely to withdraw anytime soon.

"The one thing I've learned from this trip is that we're a long way away from being able to leave. That is, if the Iraqi people want us to stay, we're gonna' be here for a while, in large numbers," Graham said. "I ask the American people to be patient, because what happens here will affect our security back home."

McCain said the key issue wasn't how long the U.S. military would stay, but rather, bringing down the number of casualties while they're here.

U.S. troop deaths are reported nearly every day. One soldier died Friday in a suicide bombing.

As of Friday, at least 1,475 members of the U.S. military have died since the U.S. invaded in March 2003, according to an Associated Press count.