Two non-proliferation experts say the United States and the European Union must raise the stakes with Iran over its suspected efforts to develop nuclear weapons.  The experts briefed members of Congress and others on Capitol Hill

The central message is that regardless of an internal debate both believe is ongoing within Iran about nuclear weapons, the United States and Europe have not made clear to Tehran that there would be huge consequences if proceeds to develop weapons.

In a word, that means sanctions.  Kenneth Pollack, former CIA analyst and author of a new book on Iran, says the agreement between Iran and the EU fails to achieve one important thing, communicate a credible threat.

"What we don't have is [those] sanctions," said Mr. Pollack.  "Right now, the only thing hanging over Iran's head is the question of whether they are going to get all these goodies the Europeans offer them, or not get those goodies.  The choice they have is status quo, which they're not terribly happy with, but is not catastrophic for them, or this much rosier future."

Mr. Pollack says the agreement with the EU does not provide those within Iran who may oppose development of nuclear weapons with a powerful enough tool to overcome the views of those who favor it.

Both Mr. Pollack, and David Albright, a physicist and former arms inspector, referred to comments by Secretary of State Colin Powell that Iran appears to be going ahead with efforts to develop nuclear weapons.

Mr. Albright cautions against drawing any conclusions at this point, recalling the controversy about alleged weapons of mass destruction programs in Iraq.

"Secretary of State Powell's remarks [Wednesday] about evidence of, basically an attempt to put a nuclear warhead on a missile may refer to a previous time, may be ambiguous, so I would caution against definitive comments about the status of the Iranian nuclear weapons program, that there is a lot of uncertainty about that," said Mr. Albright.

Mr. Albright says the United States and Europe, backed by what he calls a worldwide consensus against Iranian possession of nuclear weapons, need to embark on a long-term strategy of directing Iran's ambitions away from fuel development for weapons purposes.

On the efforts of the International Atomic Energy Agency, both experts agree it will need more time to resolve issues relating to Iran's nuclear program.

Mr. Albright says much of the criticism of the agency has been unfair.  But he adds that the IAEA still has one major job ahead of it, to interview Pakistani nuclear scientist A. Q. Khan about possible transfers of nuclear material to Iran.

"It may be unachievable, but it is very important that the U.S. put pressure on Pakistan to allow this, because you cannot trust the Pakistani government in the end to represent what A.Q. Khan says and you have to worry about whether it's completely and unfortunately you have to worry about whether it is fully accurate," he added.

Pakistan has denied an Iranian opposition group's allegation that A.Q. Khan gave Iran enriched uranium and designs for bombs.

The experts' appearance on Capitol came as two members of Congress, Republican Christopher Shays and Democrat Ed Markey, sent a letter to Secretary of State Powell.  In it, they urge the Bush administration to release information that, in the lawmakers' words, forms the basis of any conclusion Iran is pursuing nuclear weapons.

"Can we trust Iran's commitment to the recent agreement with the E.U?" asked Mr. Markey.  "Is this the right agreement?  Can we trust the European Union? Can we trust Secretary Powell, given how wrong he was on the Iraqi nuclear weapons program?"

Referring to Iraq and the controversy over intelligence on weapons of mass destruction programs under Saddam Hussein, the lawmakers say the United States, in their words, cannot afford to be wrong two times in a row on a subject as serious as the spread of nuclear weapons.