Days before the companies were to be delisted -- and just over two weeks before Trump is to leave the White House -- the u-turn avoids a step that threatened to heighten US-China tensions further.

It is not clear why the Exchange changed its mind but it would appear it actually asked someone about Trump’s executive order and discovered that it was illegal.

Trump’s executive order was signed in November as part of his administration's push to check China's growing economic power and force the hand of an incoming administration. It would mean that his political rivals would have a huge diplomatic mess to clean up which would take some time.

The move came as a surprise and sparked confusion among officials at the US Treasury and State departments, and National Security Council and it looks like they were who the Stock Exchange asked.

However Wall Street is starting to ask why the Stock Exchange did not do that in the first place, as it did cause problems for Chinese telcos named and shamed in Trump's order.