LONDON (Reuters) - Iran has named career diplomat and ex-nuclear negotiator Majid Takht Ravanchi as its ambassador to the United Nations, state media said, as it tries to salvage a nuclear deal with world powers after the unilateral U.S. withdrawal.

Takht Ravanchi, 61, had been a senior political adviser in the office of Iranian President Hassan Rouhani since 2017. Before that, he was deputy foreign minister for European and American affairs and also served as ambassador to Switzerland.

His move to the United Nations is notable as he was among the negotiators who helped Iran reach agreement in 2015 with the United States, Britain, France, Germany, Russia and China on limiting its nuclear activity in return for sanctions relief.

But the deal was thrown into doubt last year when President Donald Trump pulled out the United States, which was concluded before he took office, saying the accord - signed before he took office - unduly favored Iran.

Other co-signatories are trying to salvage the deal and shield Iran from renewed U.S. sanctions. Rouhani, who could be weakened by damage to Iran’s economy if the deal falls apart, warned other signatories on Tuesday to honor their pledges before Tehran’s patience runs out.

On Monday, Trump designated Iran’s Islamic Revolutionary Guards Corps a foreign terrorist organization. Iran called the move “vicious” and vowed to retaliate.