U.S. Secretary of State John Kerry said on Saturday talks with Iran had made genuine progress and the time had come to make hard decisions in reaching a deal to curb Tehran's nuclear program.
Iranian President Hassan Rouhani was quoted by state news agency IRNA as saying there was "nothing that cannot be resolved" between the parties, who seek a deal by the end of June.
"In this round of talks, shared points of view emerged in some of the areas where there had been a difference of opinion, which can be a foundation for a final agreement," Rouhani said.
Speaking after week-long negotiations with Iran in the Swiss city of Lausanne, Kerry said he would meet European counterparts in London to try to resolve remaining sticking points. He said talks will resume next week to see whether a deal was possible.
"We are not rushing ... but we recognize that fundamental decisions have to be made now and they don't get any easier as time goes by," Kerry said. "It is time to make hard decisions.
The West suspects Iran of seeking the ability to produce nuclear weapons and the United Nations has imposed stringent economic sanctions on Tehran; Iran says its program is intended only for peaceful purposes, such as medical technology and nuclear energy, and wants the swift lifting of sanctions.
The talks, called to solve a dispute that has at times threatened to push the Middle East to the brink of war, are set to resume on Thursday. Israel, which views the Iranian nuclear program as an existential threat, views them with suspicion, fearing a deal allowing Tehran to retain nuclear potential.
"We have not yet reached the finish line but make no mistake we have the opportunity to try to get this right," Kerry said. "It is a matter of political will and tough decision making.
Kerry said the P5+1 group - the United States, Britain, France, Germany, Russi and China - would coordinate to reach an understanding on the major issues. As talks between Kerry and his Iranian counterpart broke on Friday after a week of negotiations, the sides appeared deadlocked over sensitive atomic research and lifting of sanctions.
"The stakes are high and the issues are complicated, highly technical, and all inter-related," Kerry said.
French Foreign Minister Laurent Fabius said his country wanted an agreement that was sufficiently robust to guarantee Tehran could not acquire an atomic bomb.
France has been demanding more stringent restrictions on the Iranians under any deal than the other Western delegations and at one point during the talks Fabius phoned his team to ensure it made no more concessions, officials said.
U.S. officials privately bristle at France’s outspoken criticism of aspects of the talks and against Washington's strategy. Officials have expressed concerns that the French might block a deal.
"France wants an agreement, but a robust one that really guarantees that Iran can have access to civilian nuclear power, but not the atomic bomb," Fabius told Europe 1 radio on Saturday.
While the talks have made progress over the past year, differences are still wide enough to potentially prevent a final deal by the end of June.
There was no breakthrough this week. Disagreements arose among the powers, with France insisting on a longer period of restrictions on Iran's nuclear work. It also opposed the idea of suspending some U.N. sanctions relatively quickly if a deal is struck.
"If the accord is not sufficiently solid then regional countries would say it's not serious enough, so we are also going to get the nuclear weapon, and that would lead to an extremely dangerous nuclear proliferation," Fabius said.