The Arizona Republican said Sunday during "Fox News Sunday With Chris Wallace" that the Illinois senator should not have said he would meet with such leaders as Iranian President Mahmoud Ahmadinejad without preconditions.

"Now, that's not to say that envoys can't talk to each other. In fact, I believe that there are both (Department of Defense) and State Department officials who have talked to lower level Iranians about their involvement in Iraq and so on," he said. "That's all permissible.

"But to say that without preconditions he would go to Ahmadinejad and sit down and negotiate I think is -- well, it shows weak judgment and, frankly, naivete."

Yet U.S. Sen. Chris Dodd defended Obama's comments, quoting former President John F. Kennedy.

"John Kennedy, I think, said it very well in 1961 in his inaugural address. You never negotiate out of fear, but you never fear to negotiate," the Connecticut Democrat said.