China says the U.S. has "further aggravated" tensions over the Iran nuclear issue.

Foreign Ministry spokesman Geng Shuang said Wednesday that China appreciated Iran's "strict implementation" of its 2015 nuclear deal, which President Donald Trump withdrew from a year ago.

Geng said China "calls on all parties concerned to exercise restraint" and avoid escalating tensions.

Geng's comments came after Washington moved to deploy an aircraft carrier and a bomber wing to confront unspecified threats from Tehran.

Iran threatened Wednesday to resume higher enrichment of uranium in 60 days if world powers fail to negotiate new terms for the 2015 deal.

A key Iranian ally and trading partner, China was a signatory to the deal and continues to support it, along with Britain, Russia, China, the European Union, France and Germany.