Exiled former Iranian lawmakers on Thursday proposed a compromise to avert conflict over Tehran's nuclear program, calling for an end to sensitive uranium enrichment and an easing of US-led sanctions.

In a letter sent to US President Barack Obama, Iran's supreme leader Ayatollah Ali Khameini and the European Union, the seven ex-MPs said that a solution to the crisis was possible if all sides sought a "win-win" outcome.

The former lawmakers, who support greater freedoms inside Iran, proposed that the clerical regime halt enrichment of uranium of fissile purities of 20 percent, a level that could be used for a nuclear bomb if further enriched.

Iran would put its 20-percent stockpile under monitoring of the UN International Atomic Energy Agency, which would carry out inspections of the nuclear program.

Iran would enjoy the right to enrichment at lower levels as well as guarantees of sufficient fuel to research reactors for peaceful use.

In turn, the United States and five other nations negotiating with Iran -- Britain, China, France, Germany and Russia -- would lay out a clear timetable to ease sanctions that the lawmakers said have caused pain in the country.

Fatemeh Haghighatjoo, a former reformist member of the Iranian parliament who lives in Boston, said that the sweeping Western sanctions helped bring Tehran to talks but doubted they would change the regime's behavior further.

"We know how these sanctions actually hurt. Even people can't get enough medicine," she said at the Woodrow Wilson Center for International Scholars.

"Anti-West sentiment will be increased if sanctions keep continuing and we will gradually lose this social capital" of the population's positive feelings toward the West, she said.

Ali Akbar Mousavi, another former reformist lawmaker who lives in the United States, said Khamenei "needs at least a small victory," such as official Western recognition of the right to enrichment at purely civilian levels.

"He wants to say to competitors... 'Look, I won and you lost,'" Mousavi said.

The United States has voiced disappointment over Iran's response to international talks and has steadily ramped up sanctions, including trying to ban all exports of oil, its key source of foreign exchange.

US-ally Israel has refused to rule out a military strike, and American officials have repeatedly said they will do whatever it takes to stop Iran getting a nuclear weapon.

Iran says that its program is for peaceful purposes. US intelligence has not concluded that the regime has taken the decision to build a nuclear bomb.

US will do what it must to stop Iran nuclear arm: Kerry
Washington (AFP) Jan 24, 2013 - The United States will not be satisfied with containing Iran but will seek to stop it from obtaining a nuclear weapon, Senator John Kerry, the secretary of state designate, pledged Thursday.

"I repeat here today: our policy is not containment. It is prevention and the clock is ticking on our efforts to secure responsible compliance," he told lawmakers at a Senate hearing to confirm him as the next top US diplomat.

Directing an appeal at Iranian leaders, Kerry urged Tehran to prove that its nuclear program is solely for domestic energy purposes.

"If their program is peaceful, they can prove it, and that's what we're seeking," he said.

Kerry stressed that under his leadership the State Department would remain committed to its dual-track policy towards Iran, which includes talks and tough global sanctions now beginning to bite deep into the Iranian economy.

But he side-stepped a question on whether he would be open to allowing the Islamic Republic to pursue a limited enrichment of uranium, saying it would be "inappropriate" to negotiate the details of any accord in the committee.

The West has charged that Tehran is trying to build a nuclear weapon, but Iranian leaders have denied the allegations, saying their uranium enrichment is purely part of a domestic energy program.

Kerry insisted Iran must fully comply with international demands to halt uranium enrichment, adding that alongside international negotiations under the auspices of the so-called P5+1 group, Washington was open to bilateral talks.

"I think everybody's very hopeful that we can make some progress on the diplomatic front now," Kerry told the hearing, called to confirm his nomination to take over from Secretary of State Hillary Clinton.

"I'd say this to the Iranians. I hope they listen. They have continually professed the peacefulness of their program. It is not hard to prove a peaceful program," he stressed.

"Other nations have done that and do it every day. And it takes intrusive inspections. It takes living up to publicly arrived-at standards."

Israel, Washington's closest ally in the Middle East, has been pressing US President Barack Obama to set a red line for Iran on the nuclear issue.

After Tuesday's elections, Israeli Prime Minister Benjamin Netanyahu is trying to build a new coalition. Those negotiations are being closely watched for indicators on how Israel's new government will handle pressing diplomatic and foreign policy issues, such as Iran.