The International Atomic Energy Agency posted a short statement on its website on Thursday in which it described its technical talks with Iranian negotiators in Tehran on Wednesday as a "constructive exchange" regarding "two practical measures under discussion."

The most serious outstanding issues appeared to be related to allegations that prior to 2003, and possibly since then, Iran conducted research on how to construct a nuclear weapon, including explosives tests.

Tehran, which has rejected the allegations, had promised to clear up the matter by last August, a deadline agreed by it and the IAEA. Eight months later, though, it is unclear how much progress has been made towards resolving the matter. In the past, Iranian officials have claimed that the alleged evidence that it had conducted research on making a bomb, including data found on a laptop in 2004, was planted by its enemies.

The IAEA's investigation into Iran's alleged past efforts to produce nuclear weapons runs parallel to negotiations between Tehran and the so-called P5+1 group, which earlier this month reached a framework agreement designed to prevent Iran from producing a nuclear weapon.

The P5+1, made up of the United States, Russia, China, France, Britain and Germany, has said that lifting economic sanctions on Iran, which Tehran is seeking in return for curbs on its nuclear program, will not take place unlessy it fully cooperates with the IAEA's investigation.

The P5+1 group is hoping turn the framework deal, reached in negotiations in the Swiss city of Lausanne on April 2, into a final agreement by June 30.

pfd/msh (Reuters, AFP, dpa)