World powers are holding the talks in a bid to bring the United States back into the deal which then-president Donald Trump walked out of in 2018.

The US reimposed sanctions against Iran, which ramped up its nuclear activities that Western powers have long feared are aimed at making a bomb. Tehran insists the nuclear drive is entirely peaceful.

"The negotiations remain difficult as we need to clarify the question of guarantees (on lifting sanctions) and the framework of control over the Iranian nuclear programme," said the French presidential official who asked not to be named.

"Nevertheless there are some indications that the negotiations could succeed," added the official, saying President Emmanuel Macron could hold telephone talks with his Iranian counterpart Ebrahim Raisi in the next days.

The comments marked a more positive tone from Paris after Foreign Minister Jean-Yves Le Drian said last week that "the negotiations cannot go on so slowly".

The European Union coordinator Enrique Mora said Friday said the talks had been put on pause until the following week, calling for "political decisions" to break the deadlock.