A framework accord signed Monday in Tehran by the UN atomic agency and Iran is only a very preliminary step towards addressing concerns about Tehran's nuclear programme, analysts said.

In particular it does very little to ease fears about the nuclear reactor Iran is building in Arak and no specific mention is made of the watchdog's long-stalled probe into alleged past efforts to develop an atomic bomb.

But at the same time, it keeps the momentum going in efforts to resolve the long-running standoff over Iran ahead of a fresh round of talks with world powers in Geneva on November 20.

"I think it is a good first step to build confidence," Kelsey Davenport, analyst at the Arms Control Association, told AFP.

He added however that it was a "limited agreement".

It requires Iran to provide the International Atomic Energy Agency within three months with information on all new research reactors and to identify 16 sites designated for the construction of nuclear power plants.

Tehran also undertook to clarify its previous announcements regarding additional uranium enrichment facilities and on laser enrichment activity within the same period.

The accord also states that Iran would provide "mutually agreed relevant information and managed access" to its Gachin uranium mine and to the heavy water production unit for its Arak reactor.

The reactor being built in Arak figured highly in talks between Iran and world powers in Geneva last week amid concerns that Iran could extract plutonium -- an alternative to uranium for a nuclear weapon -- from the spent fuel once it is working.

But the new agreement concerns only the heavy water production plant at the site.

The reactor site itself is already under IAEA surveillance, meaning that any attempt to get plutonium -- for which Iran would need a reprocessing facility -- would be noticed by the watchdog.

"The IAEA does not know right now how much heavy water Iran is actually making and they want to get a good idea about whether and how soon it is going to operate," said Mark Hibbs from the Carnegie Endowment for International Peace.

But the possible extraction of plutonium from Arak's fuel rods "is a totally separate matter," Hibbs told AFP.

'Possible military dimensions'

The accord also steers clear of detailing how and when Iran might address possible evidence highlighted by the IAEA that prior to 2003, and possibly since, Iran conducted research into how to make a nuclear weapon components.

Iran rejects the claims. For two years it has resisted IAEA requests to visit sites where these alleged activities took place as well as to consult documents and speak to Iranian scientists.

The sites include the Parchin military base where the IAEA wants to probe claims that scientists conducted tests of conventional explosives that it says would be "strong indicators of possible nuclear weapon development".

The IAEA said only on Monday that it and Iran would cooperate further to resolve "all present and past issues", while agency chief Yukiya Amano said in Tehran such matters "will be addressed in the subsequent steps".

Shannon Kile at the Stockholm International Peace Research Institute said he however believed the IAEA easing off on these questions might help "improve the tone and atmosphere" at the next six-party talks on November 20.