Iranian President Hassan Rohani said on Saturday that recent progress in the nuclear negotiations between Tehran and world powers could lead to a final agreement and all remaining issues could be overcome, state media reported. Supreme Leader Ayatollah Ali Khamenei, meanwhile, voiced distrust of U.S. efforts to reach a nuclear deal, even as Washington spoke of "genuine progress" towards an outline accord.

Iran and six world powers – the United States, Britain, France, Germany, Russia and China – have spent the past week in Switzerland trying to reach an agreement on Tehran's disputed nuclear program.

"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," Rohani was quoted as saying by state news agency IRNA. The report did not specify the shared points of view.

"I believe it is possible to reach an agreement and there is nothing that cannot be resolved," he said after visiting a rehabilitation center for wounded military veterans.

U.S. Secretary of State John Kerry on Saturday "substantial progress" has been made toward ensuring that Iran's nuclear program will not lead to weapons development. But he noted important gaps still stand in the way of an agreement.

Kerry said Saturday that the U.S. wasn't rushing for an agreement even as a March 31 deadline looms for a framework agreement. Fundamental decisions needed to be made, he said, and stressed that world powers and Iran have an opportunity right now for a diplomatic solution.

Kerry was departing later Saturday for London to meet with European allies, before returning to Washington. Talks with Iran resume next week.

France seeks tougher restrictions

Western and Iranian officials have said that the sides are very far apart, though all delegations want a deal. Iran wants all sanctions to be lifted immediately, but a European negotiator described such a step as "out of the question."

The sides also disagree on the length of a proposed halt to Iran's nuclear work, with France pushing for a lengthy moratorium.

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 French Foreign Minister Laurent Fabius phoned his team to ensure it made no more concessions, officials said.

On Saturday, Fabius said that his country wanted an agreement over Iran's nuclear program that was sufficiently robust to guarantee that Tehran could not acquire an atomic bomb.

"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," he told Europe 1 radio on Saturday.

" 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."

The Europeans and Kerry plan to meet in London on Saturday to help bridge differences, negotiators said, before a end-March deadline for a political framework agreement and a full nuclear deal by June 30. Officials have expressed concerns that France might block a deal.

Khameini strikes combative tone

Meanwhile, Iran's Supreme Leader Ayatollah Ali Khamenei accused the United States on Saturday of using economic pressure and "bullying" to try to turn his countrymen against Islamic rule, underscoring his long-held mistrust of Tehran's main negotiating partner in nuclear talks.

Amid shouts of 'Death to America', Khamenei, who has the last word on all matters of state, reiterated in a speech in northeastern Iran that Tehran would not be pressured into giving in to Western demands in the negotiations with major powers.

But the 75-year-old cleric also voiced support for the government of President Hassan Rouhani, which is conducting the negotiations, and urged any Iranians critical of its performance not to use insults, an apparent indication that the Supreme Leader continues to place confidence in Rouhani's team.

A man in the audience shouted "Death to America", a cry taken up by the crowd. Khamenei continued: "Of course yes, death to America, because America is the original source of this pressure. They insist on putting pressure on our dear people's economy. What is their goal? Their goal is to put the people against the system."

Khamenei also took to Twitter on Saturday, saying that U.S.-backed sanctions against Iran must be lifted before a nuclear deal is signed, not after.

We reject US fraudulent offer of reaching a deal w #Iran first then lifting sanctions. Lifting sanctions is a part of deal not its outcome.