Iranian Foreign Minister Mohammad Javad Zarif, who was the lead negotiator in a landmark 2015 nuclear deal with major powers, has abruptly tendered his resignation, although there was no sign President Hassan Rouhani had accepted it.

Zarif offered an apology for his “shortcomings” in the unexpected message on Instagram on Monday, with prominent members of parliament immediately calling for Rouhani not to accept the resignation.

Zarif, 59, has served as Rouhani’s foreign minister since August 2013 and has been under constant pressure from hardliners who opposed his policy of detente with the West.

“I apologise for my inability to continue serving and for all the shortcomings during my term in office,” Zarif said in the message posted on his verified Instagram account.

He thanked Iranians and “respected officials” for their support “in the last 67 months”.