"The members of the United States military are plenty smart and they are plenty brave, and the senator from Massachusetts owes them an apology," he told a campaign rally in Georgia.
Kerry has refused to apologize, saying his comment was meant to be critical of Bush and his Iraq policy, which he described as "broken."
Kerry also said his comment had been part of a "joke" that he had failed to deliver properly in his speech.
Neither Kerry nor Bush are on the ballot for the November 7 elections, but they have been busy campaigning for other members of their respective Democratic and Republican parties.
(compiled from agency reports)