Obama accuses McCain of 'losing his bearings'

That brought an angry response from McCain's campaign, which accused Obama of trying to make an issue of McCain's age.

Age is a touchy subject for McCain, who turns 72 in August and would be the oldest person to be sworn in as president if elected.

The two senators have focused more intently on one another in recent weeks as Obama has moved closer to becoming the Democratic nominee. Thursday's back and forth between Obama and surrogates for both candidates foreshadowed a likely argument for the fall campaign.

The sparring also comes the same week as Obama's decisive victory in North Carolina's primary, which brought renewed calls for Hillary Rodham Clinton to get out of the race and clear a path for him to claim the Democratic nomination and focus on McCain.

At the root of the dispute is McCain's decision to call attention to a Hamas adviser's apparent affinity for Obama. The adviser, Ahmed Yousef, said in a recent interview: "We like Obama and hope that he will win the election."

McCain used those comments in a fundraising appeal and has cited them in interviews.

Asked about the matter Wednesday during a taping of "The Daily Show with Jon Stewart," McCain said: "It's indicative of how some of our enemies view America. And I guarantee you, they're not going to endorse me."

In an interview Thursday with CNN, Obama accused McCain of trying to smear him by repeating the comments.

"This is offensive, and I think it's disappointing, because John McCain always says, 'Well, I'm not going to run that kind of politics,'" Obama said. "And then to engage in that kind of smear, I think, is unfortunate, particularly since my policy toward Hamas has been no different than his."