Trump's former ambassador to Vietnam highlighted the main reason China may hesitate to strike a trade deal with the U.S.

The bad news is that China, perhaps not surprisingly to some, has totally violated its agreement with us," said Trump.

But a U.S. official told Reuters that it appears China was moving slowly on promises to issue export licenses for rare earths minerals. The deal called for China to lift trade countermeasures that restrict its exports of the critical metals needed for U.S. semiconductor, electronics and defense production.

JPMorgan Chase CEO Jamie Dimon sounded a warning Friday on the fractious US relationship with China — and on “the enemy within.”