Iran dismissed a last-minute offer from the Trump administration for talks, saying it could not negotiate while Washington had reneged on a 2015 deal to lift sanctions in return for curbs on Iran's nuclear program.
On Monday, Trump signed an executive order re-imposing sanctions on Iran to levy "maximum economic pressure" on the Islamic Republic.
"China's commercial cooperation with Iran is open and transparent, reasonable, fair and lawful, not violating any United Nations Security Council resolutions", it added in a faxed statement to Reuters. "They can't think that Iran won't export oil and others will export".
Despite not saying which consequences the USA will face in his latest statement, Iran had previously warned it could block the Strait of Hormuz, widely used by the regional states to export their oil and gas, as a comeback against the sanctions.
The US president said on July 30 that he is ready to meet his Iranian counterpart, Hassan Rouhani, "any time they want to".
President Donald Trump on Tuesday warned that firms doing business with Iran would be blocked from the US market as new sanctions hit the country despite appeals from Washington's allies.
European countries have also vowed to protect the nuclear deal by continuing to trade with Iran.
Zarif said in his Wednesday remarks that the world was taking Iran's side in the face of U.S. acts.
Few American companies do much business in Iran so the impact of sanctions mainly stems from Washington's ability to block European and Asian firms from trading there. Turkey buys an estimated 9.5bn cubic metres of gas from Iran.
"An worldwide consensus against the United States move has been shaped", he noted.
The top Iranian diplomat said the Americans need to be answerable to the Iranian people in numerous cases, adding that given the deep distrust the USA has caused over the past decades, the Iranians can hardly find a reason to talk to them.
Since it unilaterally pulled out of the deal in May, Washington has told other countries that they must halt all imports of Iranian oil from November 4, or face U.S. financial measures.
Trump's National Security Adviser John Bolton told Fox News that the U.S. policy "is not regime change, but we definitely want to put maximum pressure on the government".
North Korea's foreign minister Ri Yong Ho on Wednesday met with the Iranian President in Tehran on the second day of an ongoing trip to the country, Iranian state news outlets reported, with Rouhani stressing the DPRK should not place excessive trust in American commitments.
"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".
The renewed US sanctions go into effect as protests escalate against Iran's hardline ruling party over its huge military spending, which has crippled an already weak Iranian economy.