The Islamic republic is locked in negotiations with world powers to revive a 2015 deal that offered it sanctions relief in return for curbs on its nuclear programme.

The deal known formally as the Joint Comprehensive Plan of Action, or JCPOA, was designed to prevent Iran from acquiring a nuclear arsenal -- a goal it has always denied pursuing.

Tehran's chief negotiator Ali Bagheri tweeted that "we are closer than ever to an agreement" late Wednesday, hours after France warned that Iran had just days left to accept a deal.

In comments aired by state television on Thursday, Khamenei said Iran "has to think about tomorrow" and that "sooner or later we will urgently need peaceful nuclear energy".

"You can notice how the enemy alliance is pressing cruelly our nuclear issue," the supreme leader said.

"They have imposed sanctions on our nuclear energy, when they know very well that it is peaceful.

"They claim Iran will produce the bomb in some time, absurd words that make no sense and they know it very well themselves," said Khamenei.

"They know we are not looking for nuclear weapons, but for the peaceful use of nuclear energy.

"They are pushing to prevent the Iranian nation from achieving this significant progress."

Iran has always denied seeking atomic weapons even though it reneged on some of its nuclear commitments after the United States withdrew from the accord in 2018 under then president Donald Trump.