"The Iran nuclear issue is very complicated. We cannot expect that everything will come overnight, that is why we have taken a step-by-step approach," International Atomic Energy Agency head Yukiya Amano said.
"All other issues that are not contained in the annex (to Monday's agreement) will be addressed in the subsequent steps," he said at Vienna airport after arriving back from Tehran.
The framework deal agreed yesterday requires Iran to provide the IAEA within three months information on all new research reactors and to identify 16 sites designated for new nuclear power plants.
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.
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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.
But the accord 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.
A new meeting with the IAEA is scheduled for December 11.