WASHINGTON: The United States must erase any doubt over its commitment to Middle East democracy amid the “Arab Spring” that has brought dramatic but unstable change to the region, the top US Republican said Monday.

Speaking before the powerful pro-Israel lobby AIPAC, House Speaker John Boehner told the 10,000 assembled delegates that it was “delusional” for anyone to think the West could stop a nuclear-armed Iran, whose menace he said casts a shadow over the region.

Boehner, whose Republican party aims to oust President Barack Obama from the White House in 2012, was quick to assure the pro-Israel audience that the cause of Israel's security had his “100 percent support.” A day earlier, Obama addressed the annual American Israel Public Affairs Committee Policy Conference.

While he didn't mention the president's Middle East policy directly, Boehner clearly took a jab at the administration over its handling of momentous recent events there.

“We should make it clear - clearer than it has been for the last two years -- that America is on the side of those who yearn and struggle for their freedom,” Boehner said in prepared remarks.

“America's commitment to the advancement of democracy in the Middle East remains critical.” With dictatorships tumbling in Tunisia and Egypt, civil war engulfing Libya and violent demonstrations shaking Syria and Yemen, Boehner stressed that the popular uprising mark an “overdue rejection of corruption and police states.”” But now we are witnessing a battle for the region's political identity,” he continued.

“Will they now build governments that respect human life and dignity, that uphold human rights and where the people rule or will we see women and religious minorities repressed and fundamental rights abridged?”Boehner issued a warning on Tehran's nuclear ambitions, saying the Islamic republic was taking notice of how Washington has responded to Libya - “versus how it has responded to North Korea,” an Asian nuclear power whose years of threatening behavior have flummoxed the United States.

“If anyone here still doubts the Iranian regime's quest for nuclear weapons, I think you're awfully optimistic,” he said. “And if anyone here thinks we can contain the aggression and the terrorist subversion of a nuclear-armed Iran, you may not just be optimistic -- it may be delusional.”US politicians of all stripes regularly attend AIPAC conferences to voice support for the Jewish state.

More than 350 US senators and representatives were in attendance Monday night, according to AIPAC. Israeli Prime Minister Benjamin Netanyahu was due to address them later.

On Tuesday, thousands of delegates will head for meetings on Capitol Hill, where they will lobby all 100 senators and nearly all 435 representatives, pressing them to assure US aid to Israel and tighten sanctions on Iran.