Iran’s Foreign Minister Mohammad Javad Zarif has said he is stepping down, in a surprise announcement posted to his Instagram account.
He apologised for “shortcomings” during his time in government.
Mr Zarif played a prominent role in negotiating the landmark 2015 nuclear agreement between Iran and major international powers.
But the future of the deal has been put into doubt after US President Donald Trump ended US involvement.
Mr Zarif’s resignation was confirmed by Iran’s state-run news agency, IRNA, which cited a spokesman for the foreign ministry.
Why has he quit?
It is far from clear. His post on Instagram thanked the Iranian people and authorities but gave no reason for the resignation.
“I apologise for not being able to continue in the post and for all the shortcomings and flaws in the period,” he wrote.
Unlike other major social media networks, Instagram is not blocked in Iran.
It is not clear if his resignation will be accepted by President Hassan Rouhani.
Mr Zarif has been under pressure at home from hardliners since the US withdrew from the Iranian nuclear pact.
On Monday Syrian President Bashar al-Assad met Iran’s supreme leader Ayatollah Ali Khamenei but analysts noticed that Mr Zarif did not attend discussions.