Iran and P5+1, the six world powers (the UN Security Council five permanent members - Russia, China, France, the United States and the UK - and Germany), will not be able to consolidate the final document by November 24, a source at the talks told TASS on Saturday.
"There seems to be few chances to reach an agreement by Monday," he said.
The source said that "gaps in the positions on key issues remain substantial" and "the problems are the same - sanctions and (uranium) enrichment."
Iran says it needs nuclear power to generate electricity, but Western powers led by the United States claim Iran's eventual aim is to create nuclear weapons.
A plan of joint actions designed for a year that underlay the current negotiating process was agreed by Iran and the six international negotiators in Geneva on November 24, 2013. It in particular envisioned that Iran will get rid of half of accumulated uranium enriched to 20% and will dilute the second half to the 5-percent mark.