And now Trump says, according to the BBC website:

"A trade deal between the US and UK "will absolutely be possible", Donald Trump has said, hours after he told the Sun Theresa May's Brexit plan could kill an agreement.
...
He said: "I read reports where that won't be possible, but I believe after speaking with the prime minister's people and representatives and trade experts it will absolutely be possible".

So he thinks a deal is possible under the terms of the white paper.

Of course, that is only now. What he will think in a few hours time is anyone's guess.