U.S. President Donald Trump on Friday said China had violated an agreement with the U.S. to mutually roll back tariffs and trade restrictions for critical minerals and issued a new veiled threat to get tougher with Beijing.

What deal Trump was referring to was not clear. But the rhetoric was a sharp break from recent optimism when he lowered his 145% tariffs on Chinese goods to 30% for 90 days to allow for talks. China also reduced its taxes on U.S. goods from 125% to 10%.