In a significant move, Iran agreed Sunday to provide additional information sought by the U.N. nuclear agency in its long-stalled probe of suspicions that Tehran may have worked on nuclear weapons.

Iran insists it never worked — or wanted — such arms, and the U.N’.s International Atomic Energy Agency was pushing ahead with its investigation with expectations that Tehran would continue to assert that all of its activities it is ready to reveal were meant for peaceful nuclear use.

Still, the IAEA’s announcement that Tehran was ready to “provide information and explanations” for experiments in a type of detonator that the agency says could be used to trigger a nuclear explosion appeared to be the latest indication that Iran’s new political leadership is seeking to ease tensions over its nuclear program.

The agency mentioned its concerns about detonator development three years ago as part of a list of activities it said could indicate that Tehran had secretly worked on nuclear weapons. The technology had “limited civilian and conventional military applications,” it said back then, adding: “given their possible application in a nuclear explosive device … Iran development of such detonators and equipment is a matter of concern.”

Nuclear physicist Yousaf Butt welcomed the agreement as a “positive development. ” At the same time, Butt, who often questions the methods and conclusions of the IAEA probe, said that such detonators are commonly used in oil extraction and related work. As such, he said, experiments with them should not be surprising in oil-rich Iran.

But David Albright, whose Institute for Science and International Security is often consulted by the U.S. government on proliferation issues, said the concession by Iran could “crack open the door” and lead to a resolution of the allegations that it worked clandestinely on atomic arms.

The detonator issue was not on top of the list of the 2011 IAEA report of possible nuclear weapons concerns, with the agency mentioning other suspected activities that it said appeared to have had no civilian applications.

As the two sides met over the weekend in Tehran, diplomats told The Associated Press that Iran now was ready to address agency questions about its suspected nuclear weapons work after years of dismissing the issue as based on fabricated U.S. and Israeli evidence.

But they also said that the process would get underway only slowly. The fact that the Iranians were ready to engage on the detonator issue first reflected caution by both sides after more than six years of stalemate on the probe, with the agency focused on a step-by-step approach, starting with less sensitive issues and progressing to the arms-related queries.

The process began after the two sides reached an agreement three months ago that gave the agency access to several previously off-limit sites not directly linked to any suspected weapons activities.

An IAEA statement Sunday said Iran had complied with the first steps of that deal and both sides on the weekend signed off on an additional “seven practical measures.” Beyond the detonator experiments, they included Iranian agreement to provide “mutually agreed relevant information” on a site where Tehran experimented with laser uranium enrichment as well as a visit to the site where such work took place.

Iranian experts abandoned the experiments years ago and opted instead to develop their centrifuge-based enrichment program. The IAEA reported in 2008 that the laser facilities had been taken over by a private company that said it had no plans to enrich uranium.

Three years later, however, then-Iranian President Mahmoud Ahmadinejad asserted that Iran still possessed uranium laser enrichment technology — a claim that the IAEA has not been able to prove or disprove.

While uranium enrichment is not directly linked to the IAEA’s weapons probe, any hidden enrichment work would be a key worry for the United States and its allies. Iran says it is enriching only to make reactor fuel, but uranium enriched to weapons-grade levels is used as the payload of nuclear missiles.

Washington and five other world powers are meeting Feb. 18 with Iran in Vienna as they work to turn a first step agreement into a pact that permanently curbs Iran’s uranium enrichment in exchange for a full lifting of sanctions on the Islamic Republic.

Both sides say those talks are off to a promising start. But the U.S. and its allies also are looking to the IAEA-Iran meetings for additional signals that Iran is serious under its new political leadership in wanting to ease tensions over its nuclear program.

The agency is seeking access to individuals, documents and sites linked to alleged nuclear weapons-related work. Among the suspected activities are:

— indications that Iran has conducted computer modeling of a core of a nuclear warhead.

— suspected preparatory work for a nuclear weapons test, and development of a nuclear payload for Iran’s Shahab 3 intermediate range missile — a weapon that can reach Israel.

—information that Iran went further underground to continue work on nuclear weapons development past 2003, the year that U.S. intelligence agencies believe such activity ceased.

(AP)