Iran's leadership has been sharply criticized in congressional hearings on Capitol Hill, as lawmakers assess what steps the United States, Europe and others can take to avert a nuclear-armed Iran. The criticism, and testimony by experts, came amid Iranian warnings regarding what it calls U.S. aerial intelligence-gathering efforts, as well as European calls for stepped up diplomatic efforts.

Two committees spent the better part of Wednesday hearing from experts on the pros and cons of diplomatic efforts, and possible military options.

Many lawmakers are urging more pressure on Iran over its nuclear program and human rights issues.

Henry Hyde, Republican chairman of the House International Relations Committee, said the United States and Europe must make clear to Tehran what the stakes are. "Given Iran's record of active, recent, gross misbehavior, Iran merits greater scrutiny and a tougher deal. What is critical is that we and our European friends must arrive at a very clear understanding of the consequences for Iran if and when these negotiations end in failure or if Iran once again fails to live up to its promises," he said.

Mr. Hyde says consequences must be real and not rely on mere referral to the United Nations Security Council.

Even more pointed comments came from Congressman Tom Lantos. Saying elements of Iran's leadership share what he calls the martyr complex fueling terrorism in the Middle East, he adds a nuclear-armed Iran would be a regional threat the United States and others must oppose. "The ayatollahs of terror must not be allowed to acquire nuclear weapons. We must keep the pressure on Iran, as we did on Libya, to step off this most dangerous path," he said.

Experts generally agreed the United States needs to develop what one witness called a more creative and dynamic policy toward Tehran.

Mark Palmer, a former State Department official, supports a stronger effort by Washington, similar to the role the U.S. played in Ukraine, to undermine the control clerical rulers have over Iranians. "We need to get behind the democrats and dissidents in Iran. We really see that as the solution. We have had an orange revolution (in Ukraine), perhaps a green revolution now in Iran, we need to find all the ways we can to support and encourage the Iranian people to stand up for their rights," he said.

Mr. Palmer adds that U.S. efforts should include appointment of a senior White House official to focus on Iran, and should include the threat of smart, targeted sanctions.

Gary Sick, who served in the National Security Council in the administrations of Presidents Ford, Carter and Reagan, believes there is still time to head off development of an Iranian nuclear weapon.

But he warns any possible U.S. military attack, while it might set back Iran's nuclear development, would almost surely threaten those in Iran pushing for reform. "There is a very good chance that a U.S. military attack on Iran would be the one thing that would shut down the internal opposition, and give the hardline government the chance it wants to relinquish any pretext of democracy or concern for human rights," he said.

Henry Sokolkski, director of the Nonproliferation Policy Education Center, calls for a 10 to 15 year strategy to deal with a potential nuclear-armed Iran.

He believes Tehran does not yet have nuclear weapons, and expresses concern about what he calls an over-emphasis by policymakers not only on what Iran might do if or when it does have them, but also on extreme options to avert that. "In focusing on these extreme scenarios, U.S. policy planners have been drawn to acute options, such as bombing, invasion, and various forms of appeasement, that ultimately are only likely to make realization of the worst of what Iran might conceivably do with its nuclear capabilities, more probable," he said.

The expert testimony, and a separate hearing focusing on Iranian support for terrorism and human rights violations, came as Democratic and Republican lawmakers step up calls for action regarding Iran.

Some lawmakers favor legislation to support Iranian dissident groups, and proposals to put the United States on record explicitly backing regime change, modeled on similar action regarding Iraq before the ouster of Saddam Hussein.

Lawmakers also want the Bush administration to make clear to Tehran it must end its support for terrorist groups and what one lawmaker calls its continued disruption of Middle East peace efforts.

In their remarks Wednesday, expert witnesses also called for expansion of U.S. radio broadcasts to Iran by Voice of America and greater U.S. support for U.S.-based Persian language satellite broadcasters.

Meanwhile, as Wednesday's hearings were getting under way, Iran and Syria announced they will form a united front to confront threats from other countries.