A nuclear-armed Iran would be a nightmare scenario marking the death knell of the Arab-Israeli peace process and global non-proliferation efforts, experts said Monday as US lawmakers sought tighter sanctions.

As the European Union beefed up its own sanctions regime on Tehran, US Senator Mark Kirk and others unveiled a bill that would boost enforcement of existing sanctions, bring fresh pressure on Iran's oil sector and military, and shine a spotlight on the regime's poor human rights record.

The bilateral legislation, called the Iran, North Korea and Syria Sanctions Consolidation Act of 2011, aims to increase pressure on companies still doing business with Iran's energy industry, notably Chinese firms that are on existing US lists of violators but have not been sanctioned.

"What we ought to do is enforce the sanctions that are already on the books," Kirk told the annual meeting of the powerful pro-Israel lobby AIPAC.

The bill would expand an asset freeze on companies selling conventional military goods or technology to Iran, North Korea or Syria, and would also "put forward dramatically tougher sanctions against Iran's Republican Guard," he added.

The sanctions, which need congressional approval, would also target Iranian banks involved in such sales.

Brad Gordon, a former CIA analyst on Iran and now the director of policy and government affairs for the American Israel Public Affairs Committee, said Washington must come down harder on violators, pointing to a steady rise in refined petroleum deliveries to Iran in recent months after a sharp drop last year following introduction of sanctions by US President Barack Obama.

"If you don't pull the trigger on a sanction that's meaningful, eventually companies get the notion that we're not serious about this and begin to go back in," Gordon told the AIPAC delegates.

New sanctions, he said, "allows us to refocus attention on Iran" in the midst of dramatic changes in the Middle East, including the sweeping away of dictatorships in Tunisia and Egypt, civil war in Libya and unrest in Syria and Yemen that have dominated foreign policy debate.

"Tehran acquiring the bomb," he said, "is very likely the death knell of the peace process," with Israel hamstrung on making concessions on the West Bank, "knowing that Hamas backed by Iranian nuclear weapons could take over."

He said a nuclear arms race in the Middle East would mean 60 years of US efforts to contain nuclear weapons "will be in vain," and the chances of nuclear terror would increase "exponentially."

Former Israeli deputy national security adviser Chuck Freilich said that with some dozen Arab countries already announcing "civil" nuclear programs of their own, "a multi-nuclear Middle East is a nightmare which the world does not know how to deal with."

Unlike the US-Soviet confrontation, a possible Iran-Israel face-off and a nuclear Middle East "doesn't threaten the very future of humanity," Freilich said.

"But in terms of the political complexity... the US-Soviet confrontation really pales in comparison."