MINNEAPOLIS — Senator McCain wasn’t the only candidate reaching out to conservatives last night.

While Mr. McCain accepted the Republican presidential nomination, his Democratic rival, Senator Obama, was talking tough on foreign policy in a long-awaited interview with a Fox News host, Bill O’Reilly.

Mr. Obama appeared on “The O’Reilly Factor” for the first time last night and told the commentator that the surge of American forces in Iraq had “succeeded beyond our wildest dreams.” He also said that a nuclear Iran was “unacceptable” and that as president he would “never take military action off the table.”

The Democratic nominee’s interview followed months of goading by Mr. O’Reilly, and his initial appearance came on a night when the political world was focused on Mr. McCain’s acceptance speech. Fox News aired the first part of the interview, focusing on national security, last night, and the network plans to broadcast subsequent sections next week. Mr. Obama’s former rival, Senator Clinton, appeared on the show during the height of their fierce nomination battle as she sought to woo more conservative, working-class Democrats.

Mr. Obama’s clear acknowledgment of the success of the surge appeared to be the furthest he had gone in praising the decision to send in more than 20,000 additional American troops to the battlefield. A vocal opponent of the strategy, he had previously offered a much more nuanced position, recognizing the tactical military gains by American troops while contending that the surge had failed because those gains were not accompanied by political reconciliation.

The equivocating had drawn sharp and sustained criticism from Mr. McCain and the Republicans, who accused Mr. Obama of stubbornly refusing to acknowledge the increased security in Iraq and the drop in American casualties.

“I think that the surge has succeeded in ways that nobody anticipated, by the way, including President Bush and the other supporters,” Mr. Obama said last night after persistent pressure from Mr. O’Reilly to “admit” he was wrong in opposing the strategy. He added that the surge had “succeeded beyond our wildest dreams.” Mr. Obama did not retreat from criticism of the Iraqis, however, and he characterized his position on the increase in troop levels as consistent. “We have reduced the violence, but the Iraqis still haven’t taken responsibility,” he said. “And we still don’t have that kind of political reconciliation.”

His assertion that “nobody” had anticipated the success of the surge drew a sharp rebuttal from a McCain spokesman, Michael Goldfarb, who noted that the Arizona senator had been one of its top boosters. “Senator Obama should speak for himself,” Mr. Goldfarb said. “John McCain advocated for this strategy precisely because he anticipated it would succeed, while Barack Obama worked to legislate defeat.”

In the interview, Mr. O’Reilly also asked Mr. Obama whether he believed America was engaged in a war on terrorism. “Absolutely,” Mr. Obama replied. He identified the nation’s enemies as: “Al Qaeda, the Taliban — a whole host of networks that are bent on attacking America, who have a distorted ideology, who have perverted the faith of Islam, and so we have to go after them.”

Mr. Obama’s answers were notably more resolute than his foreign policy statements in other settings, where he often places more emphasis on diplomacy and less on confrontation.

He also sought to offer reassurance on Iran — an issue on which he has drawn criticism from Republicans for his stated willingness to meet with its leaders “without preconditions.”

“It is unacceptable for Iran to possess a nuclear weapon; it would be a game-changer,” Mr. Obama told Mr. O’Reilly, adding: “I have also said I would never take military action off the table.”

He refused to say what preparations he would make for possible military action against Iran, saying it would be inappropriate to tip his hand.

Before the Fox News interview aired, Mr. Obama responded to Wednesday night’s onslaught of attacks on his candidacy at the Republican National Convention. He said the opposition was focusing on him because it had few substantive proposals to offer. “By the way, I’ve been called worse on the basketball court. It’s not that big a deal,” he said.

He used another basketball reference to dismiss suggestions from Republicans that their vice presidential nominee, Governor Palin of Alaska, was being treated differently because of her gender. “If they want to work the refs, they are free to do so,” Mr. Obama said. “The notion that many questions about her work in Alaska is somehow not relevant to her potentially being vice president of the United States doesn’t make too much sense to me.”

He also cited his more than a year and a half on the campaign trail to suggest that he had the experience of being vetted by the public, as opposed to Mrs. Palin. “I assume she wants to be treated the same way guys are treated, which means their records are under scrutiny,” Mr. Obama said. “I’ve been through this for 19 months. She’s been through this for, what, four days so far?”