World powers agreed Friday to try to bring Iran to the nuclear bargaining table with a repackaged set of incentives to accompany the possibility of new sanctions.
Diplomats said the offer was meant to remind Tehran that talks were still an option.
Although the new offer contained only a few sweeteners, diplomats in Washington said they hoped it would be enough to elicit a fresh look at a time when economic sanctions appeared to be exacting a greater toll on Iran.
A Western diplomat who spoke on condition of anonymity in keeping with protocol, said the offer was a "slightly refreshed and updated version."
He said it contained all the elements of a 2006 offer, including assistance in building civil nuclear reactors, a guaranteed supply of nuclear fuel, cooperation in nuclear research, and various political and economic incentives.
The text of the offer being made by the United States, Britain, France, Russia, China and Germany was still a work in progress.
Iran turned down the 2006 offer, saying it came with insulting strings attached, and Western diplomats were hard-pressed to say why the response would be any different now.
The catch for Iran remains that it would have to shelve its program to enrich uranium before negotiations over possible rewards began. Enriched uranium can be used for nuclear power or, at higher concentrations, for weapons.
David Miliband, the British foreign secretary, said that if Tehran did not show a new interest in negotiations, the major powers would consider further sanctions. He did not give Iran a deadline to respond.
The United Nations Security Council already has imposed three sets of financial and other sanctions on Iran.
The Iranian government insists that its nuclear program is intended only to produce energy that might help it relieve demand for electricity, but doubters say Iran could use the program as cover to build a bomb. The Bush administration has been the chief advocate of sanctions. European allies have seemed frustrated by Iran's lack of interest and U.S. zeal to push the regime harder.