The United States will ensure Israel retains "military superiority" over its adversaries as the country faces the potential threat of a nuclear-armed Iran, Defense Secretary Leon Panetta said Tuesday.

"This is an ironclad pledge which says that the United States will provide whatever support is necessary for Israel to maintain military superiority over any state or coalition of states, as well as non-state actors," Panetta told the top pro-Israel lobby in Washington, AIPAC.

He touted President Barack Obama's record of security assistance to Israel, saying the administration has "dramatically" increased military aid since Obama entered the White House in 2009.

"This year, the president's budget requests $3.1 billion in security assistance to Israel, compared to $2.5 billion in 2009," said Panetta, according to a prepared text of the speech delivered to the American Israel Public Affairs Committee.

Panetta cited advanced missile and rocket defenses and plans to deliver the new F-35 fighter jet to Israel, which he said would provide the country with "unquestioned" air superiority.

But amid growing speculation that Israel may conduct a preemptive strike on Iran's nuclear sites, Panetta made no mention of more powerful "bunker buster" bombs that Israel would need to reach some deeply buried targets.

It remains unclear if the Pentagon has provided Israel with the most powerful conventional bomb in the US arsenal, the massive ordnance penetrator (MOP), which the Air Force says could strike facilities 200 feet underground.

The Pentagon chief echoed comments by Obama on Sunday, saying the United States would not tolerate Iran obtaining nuclear weapons and was ready to take military action if necessary.

"Let me be clear: We do not have a policy of containment -- we have a policy of preventing Iran from acquiring nuclear weapons," he said to applause from members of AIPAC.