Iranian President Hassan Rouhani said on Monday a nuclear deal with the West was bound to happen and he believed it could be achieved by a November 24 deadline, Reuters reports.
"We have reached consensus on generalities and there are only the fine details to be worked out: whether we would reach an agreement within the next 40 days, if the time will be extended, etc.," the president was quoted as having told his people in a late evening address broadcast live on television.
"Of course details are important too, but what's important is that the nuclear issue is irreversible. I think a final settlement can be achieved in these remaining 40 days. We will not return to the situation a year ago. The world is tired and wants it to end, resolved through negotiations," he said.
"A nuclear settlement is certain," he said, vowing to "apply all our efforts in that direction."
Rouhani cautioned nevertheless that "a 12-year-old dilemma cannot be resolved overnight."
His comments come days after a senior Iranian negotiator said nuclear talks with world powers could be extended again if no deal is reached by the November 24 deadline.
The talks are aiming to turn an interim agreement reached last year into a permanent deal.
The talks have been stalled for months over Iran's opposition to sharply reducing the size and output of centrifuges that can enrich uranium both to levels needed for reactor fuel or the core of nuclear warheads.
Iran says its enrichment program is only for peaceful purposes, but Washington fears it could be used to make a bomb.
The Islamic Republic has been taking an increasingly aggressive line in demanding its "right" to enrich uranium, with Iranian Supreme Leader Ayatollah Ali Khamenei recently saying Iran "needs" 19 times more nuclear centrifuges than the amount being offered by world powers.
Meanwhile, members of an Iranian opposition movement revealed last week that the Islamic regime is continuing its nuclear weapon research at a secret location.
According to the Iranian resistance movement in exile Mujahedin-e Khalk, also known as MEK, Tehran is developing nuclear weapons after having relocated its research facilities to avoid detection.