China said Wednesday it opposed "unilateral" sanctions against Iran, after US President Barack Obama signed into law new measures targeting the Islamic republic's central bank.
Washington's move came after the United States, Britain and Canada said in November they were slapping additional sanctions on Iran, citing evidence that Tehran is pursuing nuclear weapons.
Tehran denies the allegations, saying its nuclear programme is exclusively for medical and power generation purposes, and China has repeatedly said sanctions will not resolve the issue.
"China opposes placing one's domestic law above international law and imposing unilateral sanctions against other countries," said foreign ministry spokesman Hong Lei in response to a question about US sanctions on Iran.
China and Iran have become major economic partners in recent years, partly due to the withdrawal of Western companies in line with sanctions against Tehran.
In July last year, the two countries signed a series of agreements worth $4 billion for infrastructure projects in the water, mining, energy and industrial sectors.
Hong acknowledged that China has regular "open and transparent economic and energy interactions with Iran".
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"These interactions do not violate UN Security Council resolutions and will not impair third party interests," he said. "Therefore these interactions should not be affected."
The new US sanctions -- signed into law at the weekend -- aim to further squeeze Iran's crucial oil revenues, as most of those funds are processed by the nation's central bank.
Under the measures, foreign firms will have to choose between doing business with the Islamic republic or the economically mighty United States.
Iranian leaders and military officials have warned that such sanctions could push them to close the strategic Strait of Hormuz at the entrance to the Gulf, through which 20 percent of the world's oil flows.
Already in November, Britain said it was ceasing contact between its financial system and that of Iran, while Canada announced new sanctions targeting most transactions with Tehran.
At the time, the United States announced sanctions against Iran's energy sector and warned firms against dealing with the Islamic republic's financial sector, naming the country "a primary money laundering concern".
But China and Russia -- key allies of Iran -- have often sought to take a softer stance on the Islamic republic than their fellow members of the UN Security Council.