President Bush apologized publicly today for the humiliating treatment of Iraqi prisoners at a U.S.-run prison near Baghdad, saying photos of the abuse had made him sick to his stomach and vowing that the perpetrators would be brought to justice. But he rejected calls for the resignation of Secretary of Defense Donald H. Rumsfeld over the scandal.

In an appearance in the White House Rose Garden with visiting King Abdullah of Jordan, Bush said he and the king had talked about the "images of cruelty and humiliation" that have emerged from Abu Ghraib prison, where U.S. military police and intelligence operatives have been accused of mistreating detainees.

Bush said he told Abdullah that "the wrong-doers will be brought to justice" and that their actions do not represent American values.

"I told him I was sorry for the humiliation suffered by the Iraqi prisoners and the humiliation suffered by their families," Bush said. "I told him I was equally sorry that people who've been seeing those pictures didn't understand the true nature and heart of America. I assured him that Americans like me didn't appreciate what we saw and that it made us sick to our stomachs."

In response to a reporter's question, Bush defended Rumsfeld, who has become a target for congressional Democrats over the prisoner abuse.

"Secretary Rumsfeld is a really good secretary of defense" who has served the nation in that post during two wars, Bush said. "And he's an important part of my Cabinet, and he'll stay in my Cabinet."

Earlier, Rep. Nancy Pelosi (D-Calif.), the House minority leader, called for Rumsfeld to resign, telling reporters that he "has been engaged in a cover-up from the start on this issue." Other Democrats expressed similar views.

Sen. Tom Harkin (D-Iowa) said in a statement that Rumsfeld's statements, policies and actions had "created conditions that led to these abuses," but that Rumsfeld has refused to accept responsibility.

"For the good of our country, the safety of our troops and our image around the globe, Secretary Rumsfeld should resign," Harkin said. "If he does not resign forthwith, the president should fire him."

Rep. Charles B. Rangel (D-N.Y.) went further, saying that if Rumsfeld did not resign and Bush did not fire him, he should be impeached.

Democratic presidential contender John F. Kerry also weighed in on the prisoner abuse issue during a campaign appearance in California. The Massachusetts senator did not address the budding Rumsfeld controversy, but chided Bush over his leadership with regard to the mistreatment in Iraq.

"These despicable actions have endangered the lives of our soldiers, and they have frankly made their mission harder to accomplish," Kerry said at a high school in Colton, Calif. "We cannot succeed in Iraq by abandoning the values that define America."

If elected in November, Kerry said, "I will take responsibility for the bad as well as the good. As president, I will not be the last to know what is going on in my command. I will demand accountability from those who serve, and I will take responsibility for their actions. And I will do everything that I can in my power to repair the damage that this has caused to America's standing in the world and to the ideals for which we stand."

At his joint appearance with Bush, Abdullah said that in his country "we were all horrified by the images" of the abuse at Abu Ghraib, where photos taken by U.S. military police guards show naked and hooded Iraqi prisoners in humiliating poses or suffering other mistreatment.

One photo shows a hooded prisoner standing on a box with electrical wires attached to his body, reportedly having been told that he would be electrocuted if he fell off. Another, published in The Washington Post today, shows a female American guard holding a leash attached to the neck of a naked prisoner who is lying on the floor. The abuses depicted in the photos took place in October and November last year, according to investigators.

Abdullah, after his meeting with Bush at the White House, expressed confidence that "those that were guilty of these crimes will be brought to justice" following an investigation.

Asked about a meeting with Rumsfeld yesterday in which Bush reportedly admonished his defense secretary, the president said, "I told him I should have known about the pictures and the report." In addition to the photos showing Iraqi prisoners being mistreated and humiliated, the military in March received a report from an Army major general detailing the abuse at Abu Ghraib and recommending disciplinary actions and other remedies.

Bush said his focus now is "to make sure it doesn't happen again." He said he also wants to ensure that "there is not a larger problem" in the military prison system in Iraq and elsewhere.

"The acts were abhorrent," Bush said. "They sickened my stomach. . . . Any decent soul doesn't want a human being treated that way. It's a stain on our country's honor and our country's reputation. . . . And that's why it's important that justice be done."

Bush stressed that "the actions of the people in that prison do not reflect the nature of the men and women who wear our uniform." He added, "There are thousands of acts of kindness and decency taking place every day in Iraq, because our soldiers, our men and women in uniform, are honorable, decent, loving people."

In interviews yesterday with Arabic television networks, Bush had denounced the treatment of the Iraqi prisoners but stopped short of issuing an apology. His response was largely seen as inadequate in much of the Middle East.

The Democratic criticism of Bush came as a new poll showed public support for the president's handling of Iraq slipping to its lowest level. A survey by the Gallup Organization showed that only 42 percent of Americans approve of the way Bush is handling the situation in Iraq and that 55 percent disapprove. In a Gallup poll in January, 61 percent approved.

Approval ratings for Bush's handling of the economy, foreign affairs and the war on terrorism also dropped.

But Kerry made only a marginal gain against Bush in the latest survey. If the presidential election were held today, Bush and Kerry would each win 47 percent of the vote, with independent candidate Ralph Nader a distant third at 3 percent, the Gallup poll showed. The poll had a margin of error ranging from 3 to 4 percentage points.