Defense Secretary Leon Panetta spoke to a pro-Israel audience Tuesday. (Rebecca Nelson/Medill)

WASHINGTON — Appealing to a crowd of 13,000 pro-Israel activists, U.S. Secretary of Defense Leon Panetta reaffirmed the United States’ strong commitment to Israel and emphasized its determination to “prevent Iran from obtaining a nuclear weapon.”

“Iran will face severe and growing consequences” if it does not adhere to international rules and stop its nuclear activity, he said.

Panetta wrapped up the annual three-day conference of the American Public Affairs Committee, commonly referred to as AIPAC. His speech at the Washington Convention Center, delivered the same message heard throughout the week — there is no greater threat to Israel, or the rest of the world, than a nuclear-armed Iran.

“Let me be clear,” Panetta said. “We do not have a policy of containment. We have a policy of preventing Iran from acquiring nuclear weapons.”

Panetta’s comments echoed President Obama, who spoke at the AIPAC event on Sunday. The defense secretary stated that although the United States will continue to push for diplomacy, nothing is off the table.

“Military action is the last alternative when all else fails,” Panetta said. “But make no mistake, if all else fails we will act.”

The United States and Israel strongly disagree over whether military action is necessary to stop Iran’s nuclear development. President Obama has urged diplomacy and tougher sanctions, while Israeli Prime Minister Benjamin Netanyahu has emphasized Israel’s right to attack.

“When it comes to Israel’s security, Israel has the right, the sovereign right, to make its own decisions,” said Netanyahu during a meeting with the president on Monday. “Israel must reserve the right to defend itself.”

The Obama administration believes economic have crippled Iran’s economy and should continue to be used.

“We want diplomacy to work,” said Panetta, who described the U.S.-Israel relationship as tighter than any time during his 30 years in government.

However, the Republican presidential candidates have argued otherwise. They have criticized President Obama for failing to impose harsher sanctions on Iran and tainting the U.S.-Israel relationship.

“We’ve heard a lot of words from this administration. Its clear message has been to warn Israel to consider the costs of military action against Iran,” said Romney, who addressed the AIPAC meeting via satellite from Boston. “Israel does not need public lectures about how to weigh decisions of war and peace. It needs our support.”

Newt Gingrich and Rick Santorum also took a break from the Super Tuesday campaign trail to address AIPAC. Gingrich spoke via satellite, while Santorum spoke to the group in person.

This year’s conference was the first time presidential candidates from the  party out of power spoke in a year when the incumbent was seeking reelection. Other keynote speakers this week included Netanyahu and Shimon Peres, Israel’s president.