A few weeks later, at an Oval Office bill signing, Sherman again raised the issue, handing Bush a five-page memo detailing the steps he believes the administration should be taking.

"I've had about 10 substantive conversations with the president, and every one of them has been about Iran," Sherman said. "I could talk to him about the Santa Monica Mountains, but that could get worse."

Even for the ever-shticking Sherman, the threat posed by a nuclear Tehran is no joke. In fact, it has become one of his signature issues, leading a top aide on the House International Relations Committee to dub him "Mr. Iran."

While Congress' fears of Iran's nuclear plans have intensified in recent months, particularly in the wake of President Mahmous Ahmadineiad's call for Israel to be wiped off the map, there remains still just a small cadre of lawmakers - Sherman among them - consistently urging the administration to crack down on Iran.

"I think he's one of a few members of Congress that truly understands the nature of the Iranian regime and the kind of threats that it poses to U.S. national security," said Sam Kermanian, who heads the Iranian-American Jewish Federation in Los Angeles.

"He has a large constituency of Iranians," more than 500,000 in Southern California alone, Kermanian estimated, "and he's also pretty familiar with the larger issues of the Middle East."

Added Bob Einhorn, a veteran diplomat who serves as a senior adviser at the Center for Strategic International Studies in D.C.: "The United States Congress will always play a secondary role (to the administration) on Iran, but a handful of members of Congress who become very knowledgeable can exert a lot of influence on the direction of the administration's thinking.

"Congressman Sherman is among those members who is becoming an expert in this portfolio," he said. "He has become a very skillful and knowledgeable advocate for non-proliferation."

A longtime member of the House foreign affairs panel and the top Democrat on the non-proliferation subcommittee, Sherman has been working on Iran nuclear issues about five years.

He believes Tehran is six to 10 years away from developing a nuclear weapon, and sees that as one of the greatest threats to U.S. security. He accuses President Bush of having an "ostrich policy" on the issue, and criticized the administration both for dropping U.S. objections to Iran joining the World Trade Organization and for allowing the sale of Boeing parts so Iran can repair its aging commercial fleet.

"We have done nothing and things on the ground have gotten worse," Sherman said. "We've had all the warnings in the world. We're getting years and years of warnings. We're doing little or nothing."

Experts agree.

Einhorn said Washington has long harbored divisions between those who want to engage Iran and those who want to isolate the country, leaving the U.S. without a coherent approach. But, he noted, Ahmadineiad's recent actions have served to unite the administration.

A staunch supporter of Israel, Sherman maintained he views Iran's nuclear threat strictly in terms of America's security.

"The Iran issue is a U.S.-Iran nuclear proliferation issue with implications for Israel," he said.

While lawmakers and policy experts said they recognize Sherman as a serious player on Iran, some also said he uses the issue as a vehicle for partisan potshots at the Bush administration.

Ilan Berman, author of "Tehran Rising: Iran's Challenge to the United States," who appeared on a panel with Sherman recently on Iran, praised Sherman's substance but said they differ in "style."

Added Rep. Elton Gallegly, R-Thousand Oaks, who previously chaired the non-proliferation panel with Sherman, "Brad has a passion for this issue, and I applaud him. We agree on the policy. We just have a little different style in the way we approach it."

Sherman maintains he criticized the Clinton administration just as harshly. In 2000 he charged that there was "blood in the caviar" that the U.S. continued to import from Iran even as the trial of 13 Iranian Jews accused of espionage ensued.

"I have never said anything quite that strident about the Bush administration," Sherman said. Later, however, he suggested that by failing to pressure U.S. trade partners who also trade with Iran, like China, Bush "engages in a felony in order to protect those who do business with Iran."

He also has a severe assessment of Democrats who, he said, "are strongly suspicious of anything that sounds like an aggressive attempt to protect America."

Sherman is among 333 co-sponsors to legislation by Ileana Ros-Lehtinen, R-Fla., codifying sanctions and regulations against Iran and expanding the list of entities that could be sanctioned for doing business with Tehran.

Sherman also has his own bill, similar to one proposed by Sen. Sam Brownback, R-Kan., to end the importation of Iranian goods until Tehran has terminated its nuclear program; and discouraging the World Bank from giving loans to Iran. The bill has 22 co-sponsors and Sherman said he does not expect it to move forward any time soon.

In the meantime, he awaits word on his memo to President Bush.

Said White House spokesman Blair Jones, "We've received the letter and are taking a look at it. We appreciate Congressman Sherman's sharing his views on the matter."