"There is absolutely no divergence whatsoever in what we believe is necessary for Iran to prove that its nuclear program is going to be peaceful," Kerry said before talks with British Foreign Secretary Philip Hammond in London, AFP reported.
"The P5+1 remains united on the subject of Iran."
Kerry was to fly to Geneva on Sunday for talks with Iranian Foreign Minister Mohammad Javad Zarif.
"Positive and serious"
Iran and US top nuclear officials joined seven-nation negotiations on Saturday, which has been termed by Iran’s top negotiator "positive and serious".
Technical experts for Iran and the six nations – Britain, France, China, Russia, the US and Germany – have been meeting alongside senior political officials. But Saturday was the first time that the head of the Atomic Energy Organization of Iran, Ali Akbar Salehi, and US Energy Secretary Ernest Moniz also joined the talks.
Western officials say the US decided to send Moniz only after Iran announced that Salehi will be coming. Their presence could improve chances of a deal by fast-tracking complex technical details of Iran's nuclear program.
Iran’s Deputy Foreign Minister for Legal and International Affairs Abbas Araqchi said on Friday Iran and the United States are pursuing negotiations “closely and intensely”.
Araqchi told IRIB that he held “positive and serious” discussions with US Undersecretary of State for Political Affairs Wendy Sherman and European Union's deputy foreign policy chief Helga Schmid in the Swiss city of Geneva on Friday.
The Iranian deputy minister explained that "positive and serious" does not mean that the parties to the talks have made “extraordinary progress”, but that intense discussions are underway on the details of the nuclear issue.
Focus on details
“After one year of negotiations on all aspects and topics, we have come to a point where we should enter into [talks about] details,” the Iranian negotiator said.
Araqchi emphasized that Iran intends to clinch a final nuclear deal with the P5+1 group that includes "integrated generalities and details".
"That's the reason why we have to enter into details in all issues and at all stages," he said.
Iran and the P5+1 countries are seeking to seal a political deal by the end of March and to confirm the full technical details of the accord by July 1.
The scale of Iran’s uranium enrichment and the timetable for the removal of anti-Iran sanctions are seen as major stumbling blocks in the talks.
Iran has so far suspended some of its enrichment program in return for certain sanctions relief.