Iranian Foreign Minister Mohammad Javad Zarif, who was the lead negotiator in the 2015 nuclear deal, has announced his resignation on Instagram.

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

AP

Zarif thanked Iranians and "respected officials" for their support "in the last 67 months".

"Many thanks for the generosity of the dear and brave people of Iran and its authorities over the past 67 months," the Us-educated architect of the 2015 nuclear deal with world powers said.

He gave no specific reasons for his decision to step down.

Zarif has served as Rouhani's foreign minister since August 2013 but he has faced severe criticism from hardliners since the US withdrew from the nuclear deal in May 2018.

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A spokesman for the Iranian mission to the United Nations, Alireza Miryousefi, confirmed the announcement of the resignation.

However there was no immediate word on whether President Hassan Rouhani would accept it.

The resignation can only take effect once President Hassan Rouhani accepts it.

Zarif played the lead role in striking the deal under which Iran agreed to curbs on its nuclear program in return for the lifting of international financial sanctions.

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He came under attack from anti-Western hardliners in Iran after the United States pulled out of the agreement last May and reimposed sanctions.

Some hardliners even threatened Zarif with bodily harm after the nuclear deal was signed. Iran's top authority, Supreme Leader Ayatollah Ali Khamenei, guardedly backed the deal.