The expectations of an agreement between the international community and Iran regarding its nuclear program on Sunday were postponed for a new round of negotiations between Tehran and the G5+1 nations scheduled for Nov. 20.

"Concrete progress" has been achieved in three days of intense and constructive talks, but "differences remain," Catherine Ashton, Europe's top diplomat, said.

Ashton is taking over the leadership of these talks in the name of the G5+1 countries.

This group, comprised of the five permanent members of the U.N. Security Council - the United States, Russia, Great Britain, France and China - plus Germany, have been negotiating with Iran for five years on how to implement controls on its nuclear program to guarantee, as Iran claims, that it is for purely peaceful purposes.

Although the parties agreed not to provide any details of the matters that are on the table for discussion, different sources say that still to be resolved is the manner and level of control over Iran's nuclear activities, via the International Atomic Energy Agency, as well as the halting of its uranium enrichment activities.

Iran will receive officials from the IAEA on Monday and it is expected they will agree to broaden inspections of the Middle Eastern nation's nuclear installations.

U.S. Secretary of State John Kerry, meanwhile, said Sunday that Washington will only accept a nuclear agreement with Iran if it includes serious content and added that the government is not "blind" or "stupid" concerning a possible strategem by Iran to achieve a reduction of international sanctions without scaling back its apparent push to develop atomic weapons. EFE