Longtime adversaries Iran and the United States are set to hold talks on Saturday aimed at reaching a deal on Tehran's nuclear programme.

US President Donald Trump last month wrote to Khamenei urging negotiations, but warning of possible military action if Iran refuses.

"Far from putting up a show and merely talking in front of the cameras, Tehran is seeking a real and fair agreement, important and implementable proposals are ready," Khamenei adviser Ali Shamkhani posted on X.

He confirmed that Foreign Minister Abbas Araghchi was heading to Oman "with full authority for indirect negotiations with America", adding that if Washington showed goodwill, the path forward would be "smooth".

Ahead of the talks, Trump reiterated that military action was "absolutely" possible if they failed.

Iran responded by saying Tehran could expel UN nuclear inspectors, prompting another US warning that this would be an "escalation".

Iran has consistently denied seeking to acquire nuclear weapons.

On Friday, foreign ministry spokesman Esmaeil Baqaei said Iran was "giving diplomacy a genuine chance in good faith and full vigilance".

"America should appreciate this decision, which was made despite their hostile rhetoric," he said.

- 'Stupid actions' -

The talks were first announced by Trump during Israeli Prime Minister Benjamin Netanyahu's visit to Washington.

He said they would be high-level and "direct", but Iran insisted they would be "indirect".

"The talks will be conducted indirectly through the exchange of texts," claimed Iran's Fars news agency, without naming a source.

Araghchi and US special envoy Steve Witkoff are due to lead the talks in Oman, which has played a mediating role on the Iran nuclear issue.

Witkoff visited Iran's ally Russia on Friday for talks on Ukraine with President Vladimir Putin.

Expert-level consultations between Russia, China and Iran on nuclear issues were held in Moscow on Tuesday, Russia's foreign ministry said.

Iran has in recent months also been talking with the three European parties to the 2015 nuclear deal, Britain, France and Germany.

The 2015 accord saw sanctions relief for Iran in exchange for limits on its nuclear programme.

On Friday, the European Union cautioned that there was "no alternative to diplomacy" on the Iranian nuclear issue.

Germany urged both sides to reach a "diplomatic solution", calling it a "positive development that there is a channel for dialogue between Iran and the United States".

On Thursday, Washington imposed additional sanctions on Iran, targeting its oil network and nuclear programme.

Iran's nuclear agency chief Mohammad Eslami downplayed their impact.

"They applied maximum pressure with various sanctions, but they were unable to prevent the country from progressing," he said.

"They still think that they can stop this nation and country with threats and intimidation, psychological operations, or stupid actions."

- 'Threats and intimidation' -

Iran has been in the spotlight since Trump returned to office, and its regional allies have suffered major setbacks.

Hamas in Gaza and Hezbollah in Lebanon have suffered heavy losses in conflicts with Israel sparked by the Palestinian group's October 2023 attack.

Since the Gaza war began, Iran and Israel have attacked each other directly for the first time.

Warning of military action against Iran should the talks fail, Trump said US ally Israel would "obviously be very much involved in that, be the leader of that".

Khamenei's adviser Shamkhani said such threats could prompt the expulsion of UN nuclear watchdog inspectors.

"Transfer of enriched materials to secure locations may also be considered," he added of Iran's uranium enrichment activities.

While the West wants to include Iran's ballistic missile programme and regional influence in negotiations, Tehran maintains it will talk only about its nuclear programme.

"If the American side does not raise irrelevant issues and demands and puts aside threats and intimidation, there is a good possibility of reaching an agreement," deputy foreign minister Majid Takht-Ravanchi said.

Hardline Iranian media are sceptical about the talks.

The Kayhan newspaper warned that entering negotiations with the United States in a bid to lift sanctions was a "failed strategy".

During his first term, Trump withdrew from the 2015 nuclear deal and reimposed sweeping economic sanctions.

Tehran adhered to the deal for a year before rolling back its own commitments.