Even if Iran and the major powers can reach a framework nuclear deal by the end of this month, further serious negotiations would be needed to achieve a full agreement by June 30, a senior European diplomat said on Friday.
Iran and the six major powers resume talks in Lausanne, Switzerland, next week, in search of an agreement to place constraints on Tehran's nuclear activities for a specified period of time in exchange for the lifting of sanctions.
The six powers -- Britain, China, France, Germany, Russia and the United States -- aim to complete the framework of a final nuclear deal by the end of March and reach a full agreement by June 30.
The senior European diplomat, speaking to journalists on condition of anonymity, said it was hard to tell if next week's talks would produce a breakthrough on a framework deal, Reuters reported.
"We've really made progress, particularly in the last weeks, but there are still some very difficult issues ... Frankly, I can't tell," the diplomat said.
Key Understanding
A political agreement would be a "key understanding on where we are on the major issues -- the scope of enrichment, for example."
Asked if further serious negotiations would be needed beyond March 31, if a political framework agreement was reached by then, the diplomat said, "Yes, yes, absolutely."
"I still don't know if they (Iran) can take the final steps, frankly," the diplomat added.
The diplomat said the participation of Iran's nuclear chief Ali Akbar Salehi in some of the recent discussions had been very helpful.
Some western countries claim Iran may be seeking the capability to build a nuclear bomb, something Tehran denies, stressing that its nuclear work is only for peaceful applications.
French Foreign Minister Laurent Fabius said last week that commitments offered by Iran did not go far enough.
"As far as the volume, checks and duration of the envisaged commitments are concerned, the situation is still insufficient, so there is more work to be done," he said.
Forty-seven Republican US senators warned Iran's officials on Monday that any nuclear deal with President Barack Obama could last only as long as he remains in office.
European Union foreign policy chief Federica Mogherini will host talks in Brussels on Monday with the foreign ministers of Iran, Germany, France and Britain to discuss specific European concerns in the nuclear negotiations.
