Israel and the United States have "different clocks" regarding Iran's nuclear program, Chairman of the U.S. Joint Chiefs of Staff Gen. Martin Dempsey said on Sunday.

According to a report by the French agency, Agence France Presse, Dempsey said that Israel views the threat posed by Iran's nuclear program "more urgently" than the U.S.

"They [Israel] are living with an existential concern that we are not living with," Dempsey was quoted as saying.

Dempsey, who spoke to reporters at the start of a trip to Afghanistan and Iraq, reiterated his previous assessment that Israeli military action could delay, but not destroy, Iran's nuclear program. "I may not know about all of their capabilities but I think that it's a fair characterization to say that they could delay but not destroy Iran's nuclear capabilities," he said at a joint press briefing with Defense Secretary Leon Panetta last week.

The head of the U.S. military said that he consults with Israel Defense Forces Chief of Staff Lt. Gen. Benny Gantz on a regular basis, once every two weeks.

"We compare intelligence, we discuss regional implications. And we've admitted to each other that our clocks are turning at different rates," Dempsey said of his relationship with Gantz.

"You can take two countries and interpret the same intelligence and come out with two different conclusions. I'd suggest to you that's what's really happening here," Dempsey added.

Dempsey also said that the U.S. military felt no pressure from Israel to back possible bombing raids.

Former head of the Knesset Foreign Affairs and Defense Committee Tzachi Hanegbi on Sunday rejected comments by President Shimon Peres last week that U.S. President Barack Obama could be trusted to prevent the Islamic republic from obtaining nuclear weapons.

"I don't believe that there is any American analyst, and certainly no Israeli analyst that I know of, who thinks that the statements made up until now — whether in public by the president or his associates, or in private discussions — allow us to deduce that the Americans have committed to acting belligerently, i.e., to taking military action against Iran's nuclear program," Hanegbi said in an interview on Channel 1.

"The American president, like every cautious and restrained president, does not bind the interests of the United States to the interests of another country. They [the Americans] say they are not taking the military option off the table, but I don't see the Americans using it in the foreseeable future."

"The central principle of Israel's security doctrine since the founding of the country has been that, when there is no choice, Israel does not put matters regarding its existence into the hands of others."

Hanegbi, who recently switched back from Kadima to Likud and has reportedly become closer to Prime Minister Benjamin Netanyahu, also disagreed with Peres' assessment that Israel could not carry out independent military action against Iran.

"My position is that Israel is capable of achieving major accomplishments," Hanegbi said. "If the alternative is to accept a nuclear Iran — this is intolerable in my view."