"Such a request was made" around the time of Israeli Prime Minister Benjamin Netanyahu's visit to Washington this week, the official said, confirming media reports.
But the official, who spoke on condition of anonymity given the sensitivity of the issue, played down as "unrealistic" Israeli reports that the United States would condition supplying the hardware on Israel promising not to attack Iran this year.
White House spokesman Jay Carney, asked whether the Israelis had made such a request to U.S. officials during the visit, said "there was no such agreement proposed or reached" in President Barack Obama's meetings with Netanyahu or his aides.
But when asked if the matter was raised with Defense Secretary Leon Panetta or other U.S. officials, Carney told reporters he had no information on that. "I would refer you to other officials," he said.