Vienna, Austria ? Iran threatened the United States with “harm and pain” Wednesday if the U.S. tries to use the U.N. Security Council as a new and potent lever to punish Tehran for its suspect nuclear program.

Washington warned that Tehran has enough nuclear material for up to 10 atomic bombs.

The rhetoric reflected the intensity of the debate at a meeting of the International Atomic Energy’s 35-nation board over a critical report on Iran’s nuclear program. The meeting ended late Wednesday, formally opening the path to Security Council action that could range from a mild statement urging compliance to sanctions or even military measures.

The meeting also set the stage for a potential struggle between Washington, which seeks harsh measures against Tehran, and Moscow, which advocates a softer line.

But the head of the IAEA – the U.N. nuclear watchdog – cast Security Council involvement as a continuation of diplomacy with Iran. Mohamed ElBaradei also suggested that Washington might need to talk to Tehran directly if negotiations reach the stage of focusing on security guarantees to Tehran in exchange for concessions on its nuclear program.

The IAEA put the Security Council on alert over the issue last month but delayed any action to give more time for diplomacy under an agreement by the United States, Russia, China, France and Britain – the five permanent Security Council members that wield veto power.

At U.N. headquarters in New York, the five permanent members met for the first time Wednesday to discuss a first response to the Iran nuclear crisis. One council diplomat, speaking on condition of anonymity, said after the quick consultations that Britain had proposed that ElBaradei report back in two weeks about Iran’s progress toward compliance with IAEA resolutions.

Iran claims its nuclear program is peaceful and only aimed at generating electricity, but an increasing number of countries have come to share the U.S. view that Tehran is seeking to develop atomic weapons.