WASHINGTON - Sen. Hillary Rodham Clinton on Thursday called on Defense Secretary Donald H. Rumsfeld to resign, hours after excoriating him at a public hearing over what she called "failed policy" in Iraq.

Senator Hillary Rodham Clinton.

"I just don't understand why we can't get new leadership that would give us a fighting chance to turn the situation around before it's too late," the New York Democrat and potential 2008 presidential contender said in an interview with The Associated Press. "I think the president should choose to accept Secretary Rumsfeld's resignation."

"The secretary has lost credibility with the Congress and with the people," she said. "It's time for him to step down and be replaced by someone who can develop an effective strategy and communicate it effectively to the American people and to the world."

Asked about Clinton's comments, Pentagon spokesman Eric Ruff said, "We don't discuss politics."

Clinton had resisted joining the chorus of other Democrats demanding Rumsfeld's ouster. Her remarks Thursday were the harshest assessment yet from the woman considered her party's early front-runner for the 2008 presidential nomination.

Defense Secretary Donald H. Rumsfeld. [Reuters]

The former first lady has come under attack from some in her own party for voting for the war in 2002 and her current opposition to a deadline for U.S. troop withdrawal.

She criticized Rumsfeld in person earlier Thursday during a Senate Armed Services Committee hearing.

"Under your leadership, there have been numerous errors in judgment that have led us to where we are," she said. "We have a full-fledged insurgency and full-blown sectarian conflict in Iraq."

The defense secretary rejected some of her specific criticisms as simply wrong and said the war against terror will be a drawn-out process. He said he never glossed over the difficulties of the fighting.

"I have never painted a rosy picture," he said. "I've been very measured in my words, and you'd have a dickens of a time trying to find instances where I've been excessively optimistic."

Earlier in the day, the senator wasted no time going after Rumsfeld when he testified in a morning hearing before the Senate Armed Services Committee.

"Under your leadership there have been numerous errors in judgment that have led us to where we are," the New York Democrat said at a Senate Armed Services Committee hearing. "We have a full-fledged insurgency and full-blown sectarian conflict in Iraq."

The defense secretary seemed briefly stunned by the intensity of her attack, exclaiming, "My goodness," before launching into a point-by-point defense.

He rejected some of her specific criticisms as simply wrong and said the war against terror will be a drawn-out process.

"Are there setbacks? Yes," said Rumsfeld. "Is this problem going to get solved in the near term? I think it's going to take some time."

The testy exchange between Clinton and Rumsfeld came after a top general told the panel violence in Iraq is probably as bad as he's ever seen it and the country may be descending into civil war.

"We hear a lot of happy talk and rosy scenarios, but because of the administration's strategic blunders - and frankly the record of incompetence in executing - you are presiding over a failed policy," she said. "Given your track record, Secretary Rumsfeld, why should we believe your assurances now?"

Rumsfeld vehemently denied he'd ever glossed over the difficulties of the fighting in Iraq or elsewhere.

"There's a track record here," countered Clinton. "This is not 2002, 2003, 2004, 2005, when you appeared before this committee and made many comments and presented many assurances that have frankly proven to be unfulfilled."

"Senator, I don't think that's true," Rumsfeld fired back. "I have never painted a rosy picture. I've been very measured in my words and you'd have a dickens of a time trying to find instances where I've been excessively optimistic. I understand this is tough stuff."

At that point, the Republican chairman of the committee, Sen. John Warner of Virginia, came to Rumsfeld's defense, saying his past comments had been balanced.

Clinton still shied away from a demand made by a growing number of Democrats: a deadline for withdrawing troops from Iraq.

The disagreement between the two extended to Afghanistan. The senator specifically faulted Rumsfeld for saying in 2002 that the Taliban was gone, noting that the extremist faction has grown stronger in recent months.

He conceded violence has escalated in Afghanistan, but added, "Does that represent failed policy? I don't know. I would say not."

The defense secretary said he expected the violence there to follow a seasonal pattern and decline as winter approaches.