'Isolating Iran could boost radical and fundamentalist forces, ' he said, adding that 'chaos in Iran, as we have experienced in Iraq or Libya, would further destabilise an already troubled region'.
"China has consistently opposed unilateral sanctions and long-armed jurisdiction", the Chinese foreign ministry said in a faxed statement to Reuters, responding to questions on the new United States sanctions and Trump's threats on firms doing business with Iran.
North Korean Foreign Minister Ri Yong Ho met with his Iranian counterpart Mohammad Javad Zarif in Tehran on Tuesday, according to the Foreign Ministry's website.
The Turkish minister described the USA sanctions as "unilateral".
The US now plans on adding Iranian oil and gas to the sanctions in November this year.
USA sanctions on Iran's energy sector are to be re-imposed after a 180-day wind-down period ending on November 4.
"China's commercial cooperation with Iran is open and transparent, reasonable, fair and lawful, not violating any United Nations Security Council resolutions", it said.
"NEVER, EVER THREATEN THE UNITED STATES AGAIN OR YOU WILL SUFFER CONSEQUENCES THE LIKES OF WHICH FEW THROUGHOUT HISTORY HAVE EVER SUFFERED BEFORE", Trump wrote.
European countries, hoping to persuade Tehran to continue to respect the nuclear deal, have promised to try to lessen the blow of sanctions and to urge their firms not to pull out.
In an interview with the Iran newspaper published on Wednesday, Mr Zarif said the Trump administration's stated aim of cutting Iranian oil exports to zero was "meaningless" and "impossible".
Just one day after the U.S. issued their first set of sanctions were issued, Ms Mogherini said: "We are doing our best to keep Iran in the deal, to keep Iran benefiting from the economic benefits that the agreement brings to the people of Iran, because we believe this is in the security interests of not only our region but also of the world".
"America has zigzagged constantly, so now no one trusts them", he said.
"It's pretty clear to us that they were trying to use that exercise to send a message to us that as we approach this period of the sanctions here that they had some capabilities", Votel told reporters at the Pentagon.
Trump responded by noting that Iran could face serious consequences if it threatened the United States.
Already facing broad economic fallout as their currency implodes, Iranians are wondering how the next phase of the crisis in USA relations will play out - and what, exactly, America's long-term strategy is toward their country.
Iran has dismissed a last-minute offer from the Trump administration for talks, saying it could not negotiate while Washington had reneged on the 2015 deal to lift sanctions.