(CNN) -- The United States believes talk of military strikes against Iran´s nuclear program is "premature" and has advised Israel that an attack would be counterproductive, the chairman of the Joint Chiefs of Staff says.

In an interview aired Sunday on CNN´s "Fareed Zakaria GPS," Gen. Martin Dempsey said U.S. officials aren´t convinced Iran has decided to pursue nuclear weapons. Meanwhile, economic and diplomatic sanctions are taking a toll on the Islamic republic, he said.

"On that basis, I think it would be premature to exclusively decide that the time for a military option was upon us," Dempsey said.

The comments from Dempsey, a former Army chief of staff who served two tours of duty in Iraq, comes amid a period of saber-rattling in the Persian Gulf region. Israel has made clear that it considers a nuclear-armed Iran an existential threat and has made clear that it is pondering an attack on Tehran´s nuclear infrastructure, while Iran responded by warning it could cut off the narrow strait through which oil tankers sail in and out of the gulf.

Iran says it is producing enriched uranium to fuel civilian power plants and has refused international demands to halt its production of that fuel. But the International Atomic Energy Agency, the U.N. nuclear watchdog, reported in November that it had information to suggest Iran had carried out some weapons-related research, and U.N. Secretary-General Ban Ki-moon said it is up to Iran to disprove the allegation.

Dempsey said American officials believe an Israeli strike would delay Iran´s nuclear development "probably for a couple of years, but some of the targets are probably beyond their reach." He said he and others have had "a very candid, collaborative conversation" with the Israelis about the issue.

"I´m confident that they understand our concerns, that a strike at this time would be destabilizing and wouldn´t achieve their long-term objectives," he said. "But, I mean, I also understand that Israel has national interests that are unique to them. And, of course, they consider Iran to be an existential threat in a way that we have not concluded that Iran is an existential threat."

U.S. and European sanctions are already squeezing Iran´s economy, driving down its currency and driving up consumer prices. Israeli Defense Minister Ehud Barak called for still-tougher sanctions Saturday, telling reporters in Tokyo that accelerating the pace of sanctions would force Tehran to return to nuclear talks.

Iran proposed a resumption of those stalled talks last week. U.S. and European diplomats were still trying to gauge the sincerity of the Iranian offer, but U.S. Secretary of State Hillary Clinton called it "an important step." (© 2012 Cable News Network 02/20/12)