Agreement on the proposal, first reported by The Washington Times six weeks ago when it came under consideration, came at a meeting in London of Secretary of State Condoleezza Rice and her counterparts from Britain, France, Russia, China and Germany.

"Our meeting today has been dedicated towards taking the offer that we made in June 2006, reviewing it and updating it, and I'm glad to say that we've got agreement on an offer that will be made to the government of Iran," said British Foreign Secretary David Miliband.

In a brief statement to reporters, Mr. Miliband said that details of the package will not be made public, as was the case with the offer two years ago, which was never accepted by the Iranians. It included help with developing a civilian nuclear program.

"We very much hope that they will recognize the seriousness and the sincerity with which we've approached this issue, and that they will respond in a timely manner to the suggestions that we are making," he said.

U.S. officials, however, said they were skeptical that Tehran would accept the offer. Its condition is that Iran suspend enriching uranium, which the West says could be used to make nuclear weapons, although Tehran insists it will be used only for civilian purposes.

In the 2006 proposal, the six countries offered to provide Iran with nuclear energy, including a light-water reactor, partial ownership of a Russian enrichment facility and a five-year "buffer stock" of enriched uranium stored under the supervision of the International Atomic Energy Agency.

They also said that, if Iran suspended enrichment, they would support its accession to the World Trade Organization and help modernize Iran's telecommunications infrastructure. They also proposed "a new conference to promote dialogue and cooperation on regional security issues." The United States offered to sell Iran spare parts for civilian aircraft and promised to begin reversing nearly three decades of unilateral sanctions and participate in negotiations with Tehran.

A senior State Department official traveling with Miss Rice said that during yesterday's meeting the ministers went through the text "line by line" and "updated" it, but he declined to explain what that meant.

The official said the proposal will be presented to the Iranians "within a week" after the full text is finalized. He refused to say what channel will be used, but the chief negotiator with Iran in the past three years has been European Union foreign policy chief Javier Solana.

The Times reported on March 18 that the six countries were preparing a revised package because they wanted to be more specific about the timing of the incentives.

"It's not clear that the Iranian regime has transmitted to the Iranian people the details of the very generous and substantial offer that we made to them in 2006. In fact, it seems as though they have deliberately suppressed it," a British official said at the time.

The United States agreed to resubmit the offer in exchange for Russian and Chinese support for a third sanctions resolution against Iran in the U.N. Security Council in March. Except for Germany, the package's authors are veto-wielding council members.

The latest resolution, which followed similar measures in 2006 and 2007, calls for the foreign assets of 13 Iranian companies to be frozen and imposes travel bans on five Iranian officials. It also bans the sale to Iran of so-called dual-use items, which can be used for both military and civilian purposes.

Mr. Miliband yesterday said he hopes for a response to the incentives package "in a timely manner," but he set no deadlines.

"We believe that the rights that [Iran] seeks need to be accompanied by a clear set of responsibilities," he said. "It's in the spirit of seeking to fulfill both rights and responsibilities that we are making the new approach to Iran."