The Israeli and U.S. militaries have postponed large-scale war games, in part to avoid aggravating mounting tensions between the international community and Iran over its disputed nuclear program, Israeli defense officials said Monday.

The missile defense exercise, dubbed "Austere Challenge 12," was scheduled for April to improve defense systems and cooperation between U.S. and Israeli forces. The Israeli military confirmed in a one-line statement that the drill would be rescheduled for the second half of 2012, but did not disclose reasons for the postponement or any other details.

The defense officials who linked the deferral to Iran spoke on condition of anonymity because they weren't authorized to discuss the decision-making process. They offered no other reasons for the delay.

Thousands of American and Israeli soldiers were to take part in the exercise, which was designed to test multiple Israeli and U.S. air defense systems against incoming missiles and rockets from places as far away as Iran.

U.S. Defense Secretary Leon Panetta said last month that the drill exemplified unprecedented levels of defense cooperation between the two countries meant to back up Washington's "unshakable" commitment to Israel's security.

On Thursday, the top U.S. military commander is due to arrive in Israel for his first official trip since becoming chairman of the Joint Chiefs of Staff on Sept. 30. Iran is expected to be at the top of Army Gen. Martin Dempsey's agenda for talks with the Israelis.

Israel considers a nuclear-armed Iran to be a threat to its survival and repeatedly has hinted it could take military action against the Islamic Republic should international sanctions fail to stop Iran's nuclear development.

The Obama administration is concerned that Iran's recent claim that it is expanding nuclear operations might prod Israel closer to a strike.

Iran, which denies it is trying to develop nuclear weapons, has shown no sign it would willingly give up a project that has become a point of national pride.

Tehran insists its nuclear program is designed to produce energy, not bombs. It has threatened to block the strategic Strait of Hormuz, the passage for one-sixth of the world's oil, should international sanctions block Iran's petroleum exports.