Former US President Donald Trump abandoned the pact in 2018 and reimposed harsh sanctions, prompting Tehran to start violating some of the nuclear limits in 2019
"I am very grateful to the members of the council for the trust they have placed in me," Guterres said.
"Guterres's first term was defined by public silence regarding human rights abuses by China, Russia, and the United States and their allies," said Kenneth Roth.
France condemned the violence as "blind and deadly" and China added its voice to a chorus of international concern on Monday, calling for restraint from all sides.