China says Iran nuclear pact must be upheld

"Maintaining and implementing the comprehensive agreement is the shared responsibility of all parties," said Chinese foreign ministry spokesman Geng Shuang at a regular press briefing.

"We call on all relevant parties to exercise restraint, strengthen dialogue, and avoid escalating tensions," he said, adding that China "resolutely opposes" unilateral US sanctions against Iran.

China is one of six parties that signed a 2015 deal to lift nuclear-related sanctions on Iran in return for Tehran's agreement to rein in nuclear activities and ease fears it was seeking the capability to produce an atomic bomb.

Iran's Wednesday announcement that it would stop respecting limits on its nuclear activities is part of a package of measures in response to sweeping unilateral sanctions reimposed by Washington in the 12 months since it quit the agreement.

The renewed sanctions have had a severe effect on the Iranian economy.

Tehran has warned that if the five other parties to the agreement -- China, Britain, France, Germany and Russia -- failed to deliver on their commitments within 60 days to help Iran benefit from the deal despite the US sanctions, it would suspend other key limits set by the deal.