A renewed push from Jewish organizations for tougher sanctions against Iran is facing tough obstacles in Washington and capitals throughout the world.

American Jewish groups are aggressively attempting to rally support for isolating Iran until it ends its suspected nuclear weapons program. They are lobbying Congress, reaching out to friendly nations overseas and seeking allies in the United States.

Malcolm Hoenlein, the executive vice chairman of the Conference of Presidents of Major American Jewish Organizations, is warning that Iran is close to acquiring the knowledge it needs to build nuclear weapons.

Officials at the Anti-Defamation League have launched a campaign in support of tougher sanctions, and recently pressed the issue in a meeting in Moscow with Russian Foreign Minister Sergei Lavrov. Also, the American Jewish Committee has been meeting with foreign leaders, including French President Nicolas Sarkozy.

In the latest manifestation of the renewed push, delegates to the General Assembly of the United Jewish Communities in Nashville are expected to be asked Monday to vote on a resolution calling on federations and Jewish community relations councils to move on the Iran issue by initiating, coordinating and funding "expanded efforts aimed at both educating and mobilizing the Jewish community as well as partnering with other respected members in the broader community."

The resolution calls on federations to reach out to "elected officials, civic and religious groups, labor unions and think tanks, academics and student groups, human rights organizations and business associations."

This new push comes as Israeli and Jewish organizational leaders say stopping Iran's nuclear program is a life-and-death issue that must be addressed now.

"There is a civilian program, a secret weapons program, and Iran is expanding its ballistic missile power," Israeli Transportation Minister Shaul Mofaz told reporters here on Nov. 8.

Mofaz, who is serving as Jerusalem's lead negotiator in the U.S.-Israel strategic dialogue, said the need to isolate Iran had increased urgency. He pointed to Iranian President Mahmoud Ahmadinejad's announcement that his country is now operating 3,000 centrifuges -- the number required to enrich bomb-grade uranium.

The Israeli minister wants the U.N. Security Council to issue a third set of sanctions targeting Iran, ones that would effectively cripple the Iranian economy. Two earlier sets, targeting individuals and some companies, have not yet had an appreciable impact.

Mofaz emerged from his meeting in Washington with a U.S. pledge to set up two task forces -- one to promote Iran sanctions and the other to share intelligence on Iran.

Efforts by American Jewish groups would get a boost from legislation passed this year in the U.S. House of Representatives and under consideration in the Senate.

The bills, initiated by U.S. Rep. Barney Frank (D-Mass.) and U.S. Sen. Barack Obama (D-Ill.), would assist civil society groups seeking to divest from Iran by publicizing companies with investments in Iran and providing tort protections from investors.

Another measure approved by the House and awaiting action in the Senate essentially would criminalize dealings with any individual or entity that deals with Iran's energy sector. Such a measure would severely restrict Iranian business in a world financial system that at some point runs the bulk of its transactions through U.S. financial institutions.

The push for additional U.S. and U.N. sanctions are facing tough obstacles.

In Washington, the Bush administration opposes the bills making their way through Congress, in large part because the White House opposes any infringement on its powers.

In Europe and elsewhere, influential countries deeply involved in Iran's consumer markets -- including Germany, Italy, Russia and China -- want time to disentangle thousands of businesses that trade with the Islamic Republic before plunging into sanctions.

Jewish organizational leaders met not long ago with German Chancellor Angela Merkel, but failed to persuade her to pressure businesses in her country to pull out of Iran. German officials believe that divesting from Iran will take years.

In addition to questions over how rapidly sanctions could be adopted and implemented, several prominent lawmakers and world leaders are stepping up calls for a different approach: comprehensive negotiations between Iran and the United States on a range of issues. Among those calling for an immediate diplomatic push are Obama, a Democratic presidential candidate, and Sen. Chuck Hagel (R-Neb.), as well as Merkel.

Israeli officials and some American Jewish organizational leaders say the Iranians would simply use negotiations as a tactic for buying time, and with Iran close to obtaining the know-how needed to build a nuclear weapon, such delays cannot be tolerated.

According to this view, only a significantly tougher set of American and international sanctions will convince Iran to abandon its nuclear ambitions.

Hoenlein said that as soon as Iran develops a nuclear capacity, even if it does not immediately manufacture a bomb, the Middle East configuration changes.

"Once you have the technical obstacles overcome," he said, "the intimidation is already there," and Iran's backing of terrorists in the region will increase.