Sen. John F. Kerry, breaking momentarily from his cautious approach to turmoil in Iraq, blasted President Bush on Wednesday for running an "extraordinarily mismanaged and ineptly prosecuted war" and strongly suggested Bush is partly to blame for abuses at Abu Ghraib prison.

"They dismiss the Geneva Conventions, starting in Afghanistan and Guantanamo, so that the status of prisoners both legal and moral becomes ambiguous at best," the senator from Massachusetts told radio host Don Imus.

In his most expansive comments on U.S. mistreatment of Iraqis at Abu Ghraib, the presumptive Democratic nominee said this amounts to "major failures in command."

Asked if Kerry is assessing partial blame to Bush in the prison scandal, Rand Beers, a Kerry foreign policy adviser, said in an interview, "Undoubtedly, that kind of ambiguity, yes, is a failure of leadership."

Kerry proposed two immediate changes: Oust Defense Secretary Donald H. Rumsfeld and delay court-martial hearings for Americans charged with mistreating the prisoners.

"I think it's sort of a panicked move to try to display to the Arab world and others that we are going to, you know, do things immediately," Kerry said of impending hearings. "But I think you have to think of morale of the military and the chain of command."

Kerry said dismissing Rumsfeld during wartime would not hinder efforts in Iraq and Afghanistan, and he offered up a few candidates to replace the defense secretary: GOP Sens. John McCain (Ariz.) and John W. Warner (Va.) and Democratic Sen. Carl M. Levin (Mich.), a staunch war critic.

"If America has reached a point where only one person has the ability in our great democracy to manage the Pentagon and to continue or to put in place a better policy even, we're in deeper trouble than you think," Kerry said. "I don't accept that. I just don't accept that. I think that's an excuse. The fact is that we need a change in policy."

Kerry's latest comments come as the Democratic candidate wrestles with how aggressively to criticize the president at a sensitive moment when much of the world is watching the U.S. reaction to the prison scandal. Since pictures of the abused prisoners were plastered on television screens worldwide, Kerry has carefully avoided talking about the issue, for the most part. The candidate has held only one news conference in the past 31/2 weeks, in part to limit questions about Iraq. On Tuesday, he brushed aside several questions about the prisoners.

After learning that an American in Iraq was decapitated by men claiming al Qaeda affiliation, Kerry avoided any mention of Bush in his statements about the killing and struck a bipartisan, patriotic tone.

"I think it will harden the resolve of a lot of Americans to make certain terrorists won't get away with it, even as we move to address obvious problems that have existed in Iraq," he told reporters late Tuesday.

Some Democrats worry that Kerry is not saying enough about Iraq, which allows Bush and his allies to set the agenda and the tone of the debate. In Washington, Kerry campaign manager Mary Beth Cahill said the senator would continue to speak out on Iraq but would not be pressured into doing so, given how rapidly the story is unfolding.

"We're watching this, we're trying to find out as much about this as possible," she said, "but we're not going to rush into commenting on a national crisis."

The Bush campaign has repeatedly accused the senator of "politicizing" Iraq. Bush-Cheney chairman Marc Racicot told reporters Wednesday that Kerry is relentlessly "playing politics" and exploiting tragedy for political gain.

Racicot, for instance, told reporters that Kerry suggested that 150,000 or so U.S. troops are "somehow universally responsible" for the misdeeds of a small number of American soldiers and contractors. Racicot made several variations of this charge. But Kerry never said this, or anything like it.

As evidence, Racicot pointed to the following quote Kerry made at a fundraiser on Tuesday: "What has happened is not just something that a few a privates or corporals or sergeants engaged in. This is something that comes out of an attitude about the rights of prisoners of war, it's an attitude that comes out of America's overall arrogance in its policy that is alienating countries all around the world."

What Racicot did not mention was that Kerry preceded this remark by saying, "I know that what happened over there is not the behavior of 99.9 percent of our troops."

Kerry has spent the week talking about health care, but as he has focused on domestic issues other Democrats have rushed in to help shape the Iraq debate -- and often taking it in a direction different from Kerry's. Sen. Edward M. Kennedy (D-Mass.), a top Kerry supporter who opposed the war, criticized the administration so harshly this week that Kerry distanced himself from the remarks.

"On March 19, 2004, President Bush asked, 'Who would prefer that Saddam's torture chambers still be open?' " Kennedy said. "Shamefully, we now learn that Saddam's torture chambers reopened under new management: U.S. management."

Kerry told Imus: "He's my friend and I respect him, but I don't agree with the framing of that."

As Kerry continued his campaign swing, his advisers were making the case that Bush's $70 million ad campaign had failed to knock Kerry out of the race and that, compared with Al Gore four years ago, the Massachusetts senator is in solid shape to compete with Bush in the fall.

Armed with a series of slides showing current and past polling data nationally and in battleground states, Kerry's top advisers told editors and reporters at The Washington Post that the Bush campaign had mistakenly assumed a huge financial advantage at the beginning of March would allow it to dictate the terms of the race and shape perceptions of Kerry. Instead, they said, Kerry and Bush continue to run roughly even in national polls.

Cahill said the campaign decided at the end of the primaries, when Bush had $110 million in the bank and Kerry had barely $2 million, to spend March and April fundraising, and that the payoff was $43 million raised in March and an estimated $25 million or more in April. "We decided to step back and try to level the playing field financially," she said.

Staff writer Dan Balz in Washington contributed to this report.

Democratic presidential candidate John F. Kerry talks about his proposals for health care at a town hall meeting in Orlando.