U.S. President Donald Trump hinted Thursday that his administration may be preparing sanctions targeting Chinese banks over their links to Iran, in what would be a major escalation of Washington's attempts to isolate Tehran.

Treasury Secretary Scott Bessent this week announced that the United States was stepping up its campaign to "collapse" the Iranian government through economic sanctions and other measures.

This includes a vastly expanded threat of secondary sanctions on countries that continue to do business with Iran.

China is Tehran's biggest trading partner, particularly when it comes to oil. Chinese banks continue to handle payments related to those and other forms of trade between the countries.

Asked by reporters at an event in the Oval Office whether he would sanction Chinese banks over such transactions, Trump responded with his own question.

"Who said I'm not?" he said, cryptically. "I mean, who said I'm not? You don't know if I'm doing it. Well, I don't have to announce everything, do I?"

The U.S. Treasury has not so far issued any sanctions against major Chinese banks, although it has sanctioned several companies in mainland China and Hong Kong it accuses of aiding the Iranian government and armed forces.

Beijing said its cooperation with Iran has always been "within the framework of international law" and said it would do what is necessary ​to protect its rights.

The new measures come just weeks before Trump is scheduled to host Chinese leader Xi Jinping to maintain a fragile trade truce.