Iran said Monday it had made good on its warning that it would breach the limit, prompting US President Donald Trump to warn that Tehran was "playing with fire".

The United States withdrew from the nuclear deal last year and hit Iran's crucial oil exports and financial transactions as well as other sectors with biting sanctions.

Tehran, which has sought to pressure the remaining parties to save the deal, announced on May 8 that it would no longer respect the limit set on its enriched uranium and heavy water stockpiles.

It threatened to abandon further nuclear commitments unless the remaining partners -- Britain, China, France, Germany and Russia -- helped it circumvent sanctions, especially to sell its oil.

"China regrets the measures taken by Iran, but at the same time, we have emphasised on many previous occasions that the US's maximum pressure is the root cause of the current fraught tensions," Chinese foreign ministry spokesman Geng Shuang said at a regular press briefing.

"We call on all parties to view this from a long-term and overall perspective, exercise restraint and uphold the JCPOA (nuclear deal) together so that there won't be further escalation in the tense situation," Geng said.