An unusual coalition of interest groups from left and right is launching a drive today to head off an American military attack on Iran by pushing America into high-level negotiations with Tehran.

The Campaign for a New American Policy on Iran, which bills itself as "transpartisan," consists of more than three dozen organizations, most of them left-leaning, such as the American Friends Service Committee, the Institute for Policy Studies, and the Open Society Policy Center, which is backed by George Soros.

However, the campaign also has the backing of a smattering of right-of-center groups, including the American Conservative Defense Alliance, the Libertarian Party, and the American Cause, which is headed by Patrick Buchanan.

"The current rumor here in Washington is that Bush will attack after the November elections so it won't hurt the Republican nominee politically. Many around him say he feels he has to do something before he leaves office," a campaign organizer, Carah Ong of the Center for Arms Control and Nonproliferation, said. "Part of this is to raise the fact that a military attack is likely and it needs to be prevented."

The campaign to push for direct talks with Iran's mullahs is kicking off with a press conference this morning on Capitol Hill expected to feature the Libertarian nominee for president, Robert Barr, as well as several members of Congress, including Reps. Keith Ellison of Minnesota and Barbara Lee of California, both Democrats, and Rep. Ron Paul, who mounted a bid for this year's Republican presidential nomination. Brandishing red telephones supposed to symbolize a hotline to Tehran, the group will urge supporters to call Congress and press for talks.

The campaign's lobbying day follows close on the heels of a lobbying effort last week by the American Israel Public Affairs Committee, which encouraged its members to promote legislation that would put stricter sanctions on Iran. Ms. Ong said the timing was a coincidence.

Others involved in the talk-to-Iran campaign include a former CIA official, Philip Giraldi; a former adviser to President Reagan, Douglas Bandow; a former State Department official, Flynt Leverett, and the president and founder of the National Iranian American Council, Trita Parsi.

Messrs. Leverett and Parsi are best known for asserting that in 2003 the Bush administration essentially ignored a proposal for a "grand bargain" peace deal in which Iran proposed to normalize relations with America. Current and former administration officials have said they did not consider the proposal serious because of the diplomatic route by which it arrived and because of contradictory signs from Iranian officials.

Ms. Ong said the new campaign grew out of a meeting of liberals and conservatives in November 2007 at the headquarters of Americans for Tax Reform in Washington. A spokesman for that group said it was not involved in the Iran issue. The president of the American Conservative Defense Alliance, Michael Ostrolenk, said his group has office space in the building and borrowed the conference room for the session.

"With the Iraq war ... there was not enough left-right effort against the war to prevent it from being launched," Mr. Ostrolenk said. "Iran is not a direct threat against the United States. They are a threat against other players in the region, but as a conservative, I'm more concerned with the United States."

One advocate of a tough line toward Tehran, Michael Ledeen of the American Enterprise Institute, disputed the coalition's suggestion that America has been unwilling to talk with Iran. "We've tried everything. There's no stick we haven't brandished. There's no carrot we haven't dangled," he said. "They don't want us. They're our enemies."

Some campaign participants could draw unwanted notoriety to the effort. Last year, federal prosecutors named one member of the coalition, the Council on American Islamic Relations, as an unindicted co-conspirator in a criminal case linking the Texas-based Holy Land Foundation and Hamas. Cair denied the claim and asked a judge to strike the co-conspirator list from the public record. Jurors acquitted the defendants on some counts and could not reach a verdict on most, but Cair's motion was never ruled on.

Mr. Bandow was a senior fellow at the Cato Institute but resigned in 2005 after it was disclosed that he had taken money to write op-ed pieces favorable to clients of a lobbyist at the heart of an influence-peddling scandal, Jack Abramoff.