WASHINGTON (AP) — Colin Powell, a Republican and retired general who was President Bush’s first secretary of state, broke with the party Sunday and endorsed Democrat Barack Obama for president, calling him a “transformational figure” while criticizing the tone of John McCain’s campaign.

The former Joint Chiefs of Staff chairman said either senator is qualified to be commander in chief. But after studying both, he concluded that Obama is better suited than McCain, the standard-bearer of Powell’s own party, to handle the nation’s economic problems and help improve its world standing.

“It isn’t easy for me to disappoint Sen. McCain in the way that I have this morning, and I regret that,” Powell said on NBC’s “Meet the Press,” where he announced the endorsement and delivered a serious blow to the aspirations of his longtime friend, Arizona Sen. McCain.

But, Powell added: “I think we need a transformational figure. I think we need a president who is a generational change and that’s why I’m supporting Barack Obama, not out of any lack of respect or admiration for Sen. John McCain.”

The endorsement by Powell amounted to a stunning rejection of McCain, a 26-year veteran of Congress and a former Vietnam prisoner of war who has campaigned as the experienced, tested candidate who knows how to keep the country safe.

Powell’s endorsement has been much anticipated because of his impressive foreign policy credentials, a subject on which Obama, a first-term senator from Illinois, is weak. Powell is a Republican centrist popular among moderate voters.

At the same time, Powell is a black man and Obama would be the nation’s first black president — a goal Powell considered pursuing for himself in 1996, before deciding not to run. Powell said he was cognizant of the racial aspect of his endorsement, but said that was not the dominant factor in his decision.

Powell expressed disappointment in the negative tone of McCain’s campaign, his choice of Alaska Gov. Sarah Palin as a running mate and their decision to focus in the closing weeks of the contest on Obama’s ties to 1960s-era radical William Ayers, saying “it goes too far.”

A co-founder of the Weather Underground, which claimed responsibility for nonfatal bombings in the United States during the Vietnam War-era, Ayers is now a college professor who lives in Obama’s Chicago neighborhood. He and Obama also served together on civic boards in Chicago.

“This Bill Ayers situation that’s been going on for weeks became something of a central point of the campaign,” Powell said. “But Mr. McCain says that he’s a washed-out terrorist. Well, then, why do we keep talking about him?”

Powell said McCain’s choice of Palin raised questions about judgment.

“She’s a very distinguished woman, and she’s to be admired. But at the same time, now that we have had a chance to watch her for some seven weeks, I don’t believe she’s ready to be president of the United States, which is the job of the vice president,” he said. “And so that raised some question in my mind as to the judgment that Sen. McCain made.”

McCain seemed dismissive of Powell’s endorsement, saying he had support from four other former secretaries of state, all veterans of Republican administrations: Henry Kissinger, James A. Baker III, Lawrence Eagleburger and Alexander Haig.

“Well, I’ve always admired and respected Gen. Powell. We’re longtime friends. This doesn’t come as a surprise,” McCain said on “Fox News Sunday.”

Asked whether the endorsement would undercut his campaign’s assertion that Obama is not ready to lead, McCain said, “Well, again, we have a very, we have a respectful disagreement, and I think the American people will pay close attention to our message for the future and keeping America secure.”

Powell also said he was troubled that some Republicans — he excluded McCain — continue to say or allow others to say that Obama is a Muslim, when he is a Christian. Such rhetoric is polarizing, he said.

“He’s always been a Christian. But the really right answer is, what if he is? Is there something wrong with being a Muslim in this country? The answer’s no, that’s not America,” Powell said. “Is there something wrong with some 7-year-old Muslim-American kid believing that he or she could be president?”

Obama called Powell to thank him for the endorsement, Obama spokesman Robert Gibbs said.

“I am beyond honored and deeply humbled to have the support of Gen. Colin Powell,” Obama said at a rally in Fayetteville, N.C. “Gen. Powell has defended this nation bravely, and he has embodied our highest ideals through his long and distinguished public service. … And he knows, as we do, that this is a moment where we all need to come together as one nation — young and old, rich and poor, black and white, Republican and Democrat.”

Powell said he remains a Republican, even though he sees the party moving too far to the right. He supports abortion rights and affirmative action, and said McCain and Palin, both opponents of abortion, could put two more conservative justices on the Supreme Court.

“I would have difficulty with two more conservative appointments to the Supreme Court, but that’s what we’d be looking at in a McCain administration,” Powell said.

Powell chaired the Joint Chiefs of Staff, the nation’s top military post, during the first Gulf war under President George H.W. Bush. As secretary of state, he helped make the case before the United Nations for the U.S.-led invasion of Iraq, launched in March 2003.

Powell said the nation’s economic crisis provided a “final exam” of sorts for both candidates, suggested McCain had failed the test.

“I found that he was a little unsure as to how to deal with the economic problems that we were having,” Powell said. “Almost every day there was a different approach to the problem and that concerned me, sensing that he doesn’t have a complete grasp of the economic problems that we had.”

In contrast, Powell said Obama “displayed a steadiness, an intellectual curiosity, a depth of knowledge and an approach to looking at problems … . I think that he has a, a definitive way of doing business that would serve us well.”