(CNN) -- Former Secretary of State Colin Powell announced Sunday that he will be voting for Sen. Barack Obama, citing the Democrat's "ability to inspire" and the "inclusive nature of his campaign."
"I think he is a transformational figure, he is a new generation coming onto the world stage, onto the American stage, and for that reason I'll be voting for Sen. Barack Obama," Powell said on NBC's "Meet the Press."
Powell said he was concerned about what he characterized as a recent negative turn of Republican candidate Sen. John McCain's campaign, such as the campaign's attempts to tie Obama to former 1960s radical Bill Ayers.
"I think that's inappropriate. I understand what politics is about -- I know how you can go after one another, and that's good. But I think this goes too far, and I think it has made the McCain campaign look a little narrow. It's not what the American people are looking for," he said.
Powell, a retired U.S. general and a Republican, was once seen as a possible presidential candidate himself.
Powell said he has some concerns about the direction of the Republican Party, adding that it has "moved more to the right than I would like to see it." Read a transcript of Powell's remarks
In regard to the financial crisis, which Powell called the candidates' "final exam," Powell said McCain appeared unsteady in dealing with it, while Obama had excelled in handling the situation.
"Obama displayed a steadiness, an intellectual curiosity, a depth of knowledge," Powell said.
"He has met the standard of being a successful president, being an exceptional president," he said.
Obama praised Powell at a campaign event in Fayetteville, North Carolina, on Sunday, calling him "a great soldier, a great statesman, and a great American."
"I have been honored to have the benefit of his wisdom and counsel from time to time over the last few years, but today, I am beyond honored and deeply humbled to have the support of General Colin Powell," Obama said.
Obama called Powell earlier Sunday and thanked him for his endorsement, communications director Robert Gibbs said.
In their 10-minute conversation, Obama said he looked forward to taking advantage of Powell's advice in the next two weeks and hopefully over the next four years, Gibbs said.
During the campaign, Powell has met with both candidates and said he has a lot of respect for McCain. He said Sunday that he thinks both candidates are qualified to be president.
"It isn't easy for me to disappoint Sen. McCain in the way that I have this morning, and I regret that," Powell said.
Speaking on Fox News Sunday, McCain said he respects and admires Powell, and the announcement "doesn't come as a surprise."
"I'm also very pleased to have the endorsement of four former secretaries of state -- Secretaries [Henry] Kissinger, [James] Baker, [Lawrence] Eagleburger, and [Alexander] Haig -- and I'm proud to have the endorsement of well over 200 retired Army generals and admirals," McCain said.
Powell served as Secretary of State under President Bush from 2001 to 2005.
The possibility of a Powell endorsement has been rumored for several months.
On August 13, Powell's office denied a report on Fox News by commentator Bill Kristol that Powell had decided to publicly back Obama at the Democratic National Convention.
Powell himself brushed off queries on any potential presidential nod but told ABC News in August that he would not be going to Denver, Colorado, for the convention.
Back in February, Powell told CNN's Wolf Blitzer that he was weighing an endorsement of a Democratic or independent candidate.
Powell has offered praise for Obama, calling him an "exciting person on the political stage."
"He has energized a lot of people in America," said Powell. "He has energized a lot of people around the world. And so I think he is worth listening to and seeing what he stands for."
The former general, who has largely steered clear of politics since leaving the Bush administration, noted that the next president will need to work to restore America's standing in the world.
Powell gave the keynote address at the Republican National Convention in support of George W. Bush in 2000.