World powers negotiating with Iran over its nuclear programme are united in their search for an agreement and are not discussing an extension of the deadline, US Secretary of State John Kerry said on Thursday.
"Yes, we do want an agreement but not any agreement," said Kerry.
"We are united all of us in the P5+1," he added, referring to the grouping of the United States, Britain, France, Russia, China and Germany that are leading the talks with Iran.
Kerry is set later Thursday to join the troubled negotiations in Vienna, where Tehran has shown no sign of softening its position days before the November 24 deadline for a deal.
British Foreign Secretary Philip Hammond said on Wednesday he was "not optimistic" the mammoth accord would be finalised in time and expected another extension.
"We are not discussing an extension. We are negotiating to have an agreement. It's that simple," Kerry said. "I know that secretary Hammond is concerned about the gaps. We all are.
"Both sides are taking this process seriously and both sides are trying to find common ground. That does not mean we agree on everything.
"But it does mean we have discussed in detail the full range of relevant issues that have to be part of a durable and comprehensive agreement."
Kerry was in Paris to discuss the negotiations with French Foreign Minister Laurent Fabius and his Saudi counterpart Prince Saud al-Faisal.
"There remain some important points of disagreement and we hope they can be reduced," Fabius told reporters.
"That will depend very much on Iran's attitude," he added.
Iran and the five permanent members of the UN Security Council plus Germany have been negotiating since February to turn an interim accord with Iran reached a year ago into a lasting agreement.
Such a deal, after 12 years of rising tensions, is aimed at easing fears that Tehran will develop nuclear weapons under the guise of its civilian activities -- an ambition the Islamic republic has always denied.