China's business and energy ties with Iran do not harm the interests of any other country, the country's Foreign Ministry said, after U.S. President Donald Trump said companies doing business with Iran would be barred from the United States.
China has already defended its commercial relations with Iran as open and transparent as U.S. sanctions on Iran took effect despite pleas from Washington's allies.
In a statement released late on Friday, China's foreign ministry reiterated its opposition to unilateral sanctions and "long-armed jurisdiction".
"For a long time, China and Iran have had open, transparent and normal commercial cooperation in the fields of business, trade and energy, which is reasonable, fair and lawful," it said.
"This does not violate United Nations Security Council resolutions or China's promised international obligations, nor does it harm the interests of any other country, and should be respected and protected," the ministry added.
Using sanctions at the slightest pretext or to threaten anyone won't resolve the problem, it said.
"Only dialogue and negotiations are the true path to resolving the issue," the ministry added.
China, Iran's top oil customer, buys roughly 650,000 barrels a day of crude oil from Tehran, or 7 percent of China's total crude oil imports. At current market rates, the imports are worth some $15 billion a year.
State energy firms CNPC and Sinopec have invested billions of dollars in key Iranian oil fields such as Yadavaran and North Azadegan and have been sending oil to China.
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.
But that has proven difficult, and European companies have quit Iran, arguing that they cannot risk their U.S. business.
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.