Francis Fannon, the assistant secretary of state for the Bureau of Energy Resources, was recently in China to discuss sanctions, according to a State Department spokesperson.
His decision to withdraw from the 2015 Iran nuclear deal, formally known as the Joint Comprehensive Plan of Action (JCPOA), has led to months of rising tensions between Washington and Tehran.
But Trump, a long-time critic of the deal who succeeded Barack Obama as president past year, pulled out of the pact despite repeated assurances by United Nations inspectors that Iran is in compliance with its obligations.
Iran's currency plummeted this week in the lead-up to 7 August, when Washington is due to reimpose a first lot of economic sanctions following Trump's withdrawal from the nuclear deal.
Iranian President Hassan Rouhani has warned the US against any attempt to stop Tehran's oil trade, threatening to block the strategically important Strait of Hormuz.
In May Trump controversially pulled America out of the nuclear deal Obama agreed with Iran in 2015
Trump's policies are already putting significant pressure on the Iranian economy, although U.S. intelligence suggests they may ultimately rally Iranians against the United States and strengthen Iran's hardline rulers, officials say. "It shows they have not thought about its consequences", Rouhani was quoted as saying by state news agency IRNA while on an official visit to Austria's capital, Vienna, in July.
It has warned countries which ignore the policy will face United States sanction, even if they are American allies.
"The unilateral sanctions should be abandoned because they are counterproductive", Chinese Foreign Ministry spokesperson Hua Chunying told reporters.
Leszczynski adds that whilst a substitution of US-China trade with Russia-China or Iran-China trade would be negative for tonne miles, an expansion of Brazilian exports to China would to some extent compensate for that.
"China will continue to cooperate with Iran adhering to its worldwide obligations".
Ahead of the November 4 deadline, India, the second-largest purchaser of Iranian oil, increased its imports from the country by 30 percent last month. "Iran was hoping to sell more than 500,000 [barrels per day] of oil to India in [fiscal year] 2018/2019", the outlet wrote, citing a February statement by Iranian Oil Minister Bijan Zanganeh.