"We are not discussing an extension," Kerry said after meeting Fabius met in Paris on Thursday. “We are negotiating to have an agreement. It's that simple.”
Kerry and and restated their desire to strike a deal with Tehran before the deadline of 24 November.
But the Fabius recognised there were still “major differences”, adding that he hoped could be overcome.
"We hope that they can be bridged but that depends to a very large extent
on Iran's attitude," he said.
Kerry said he was grateful to Fabius for "his advice and counsel".
This reflects US fears that France could scupper the negotiations, as it did last year with its intransigent position over Iranian nuclear disarmament, Thierry Coville, an Iran specialist at the Institute of Strategic Studies in Paris told RFI.
Iran's Zarif put the onus on the other side, urging them not to make "excessive demands".