President Donald Trump threatened to hit China with "at least" another $300 billion of tariffs. (FILE)

U.S. President Donald Trump threatened to hit China with "at least" another $300 billion of tariffs but said he thought both China and Mexico wanted to make deals in their trade disputes with the United States.

"Our talks with China, a lot of interesting things are happening. We'll see what happens... I could go up another at least $300 billion and I'll do that at the right time," Trump told reporters on Thursday, without specifying which goods could be impacted.

"But I think China wants to make a deal and I think Mexico wants to make a deal badly," said Trump before boarding Air Force One at the Irish airport of Shannon on his way to France for a D-Day commemoration.