Iran has pledged to end years of stonewalling and provide answers on past suspicious activities to the U.N. nuclear monitoring agency probing its atomic program, an official said Friday, in a move being seen as an attempt to avoid new U.N. sanctions.

The offer, which the official said was made Thursday by top Iranian nuclear negotiator Ali Larijani to EU foreign policy chief Javier Solana, falls short of the concession sought by the international community — a promise to freeze Iran's uranium enrichment activities.

Iran refuses to consider such a freeze but the U.N. Security Council insists on it, and past meetings between the two men have made little progress on resolving the deadlock. Larijani's overture and the decision by Solana to treat the Iranian offer seriously reflected mutual recognition that the talks needed to advance on other issues or face the risk of collapse.

Secretary of State Condoleezza Rice, en route to Madrid for a bilateral visit not connected to the talks, signaled that while Washington was willing to be creative, it continued to insist that Iran cease enrichment.

"Where we've been flexible is on how we get to suspension," Rice told reporters.

She said she saw no evidence that Thursday's talks in Madrid produced any momentum, but noted that the two negotiators had agreed to met again in two weeks.

The United States wants the suspension to be permanent, leaving Iran unable to develop weapons but theoretically able to operate nuclear power stations with uranium processed elsewhere by others. The complicated, multistep process of manufacturing nuclear-ready uranium is called the fuel cycle.

"The issue is that any Iranian civilian nuclear program really can't have the fuel cycle attached to it, or the ability to perfect that technology," Rice said, something that could be worked out once Iran sat down for detailed talks.

"What we can't do is to have negotiations take place while the Iranians continue to perfect their nuclear technology and use those negotiations as cover," for possibly covert work on a bomb, Rice said.

U.N. and other officials, who demanded anonymity because they were not authorized to discuss the issue, said any decision by Iran to fully cooperate on clearing up past activities would represent a major concession.

They told The Associated Press that such a move could help the International Atomic Energy Agency wrap up years of efforts to establish whether Iran's past nuclear strivings were exclusively peaceful in nature.

"This is the first time they made such a serious offer" without preconditions, said one of the officials, adding, without elaboration that Larijani had offered "a short timetable" for providing the answers sought by the IAEA.

The officials agreed that the move appeared to be an attempt by Iran to at least delay if not avoid new U.N. sanctions. An IAEA report last week provided the potential trigger for such penalties by saying Iran continued to defy the Security Council ban on enrichment and instead was expanding its activities.

Larijani's offer appeared designed to address another main concern in that report — refusal by Iran to give answers about nearly two decades of clandestine nuclear activities that first came to light four years ago.

They include: traces of enriched uranium at a facility linked to the military, which could be a sign of a weapons program; lack of documentation on past enrichment activities, and possession of documents showing how to form uranium metal into the form of missile warheads.

Expressing concerns about years of stonewalling, the IAEA warned that "unless Iran addresses the long-standing verification issues ... the agency will not be able to fully reconstruct the history of Iran's nuclear program." That, in turns means that the IAEA "cannot provide assurances ... about the exclusively peaceful nature of that program."

Still, with the main Security Council demand focusing on an enrichment freeze, it was unclear whether the overture by Larijani would suffice to blunt the possibility of new sanctions — the third since the first set was imposed late last year.

Although Iran insists it has the right to the technology to generate nuclear power, there are suspicions it wants to make the atomic bomb.

Iran's ultimate stated goal is running 54,000 centrifuges to churn out enriched uranium for what it says is power generation. But critics say that equipment could also make enough fissile material or dozens of nuclear warheads a year.

On Thursday, Solana — representing the five permanent Security Council members plus Germany — clearly suggested he and Larijani made no headway on the enrichment dispute.

"Sometimes we are not able to move the process as we like, but in any case the atmosphere continues to be very positive," he said.