Tensions between Iran and the US have risen even since Washington pulled out of a nuclear pact last year and launched punitive sanctions against Tehran, saying it had not done enough to reduce its uranium stockpile.
Iran on Monday said it has started producing enriched uranium beyond the cap set under the 2015 nuclear accord, known as Joint Comprehensive Plan of Action (JCPOA), which now stands scrapped by the US.
The development was confirmed by the UN's nuclear proliferation watchdog, International Atomic Energy Agency.
"China regrets the measures taken by Iran, but at the same time, we have emphasised on many previous occasions that the US' maximum pressure is the root cause of the current tensions," said Chinese Foreign Ministry spokesperson Geng Shuang.
"We call on all parties to view this from a long-term and overall perspective, exercise restraint and uphold the JCPOA together so that there won't be further escalation in the tense situation," Geng added.
China, the biggest importer of Iranian's crude oil, is one of the parties to the nuclear pact and has pledged to keep the accord going.
Iran has threatened to walk out of the deal if other parties fail to help it stave off the US sanctions.
( With inputs from IANS )