Trump is now in the UK for a four day visit.
With his wife Melania, the president met British Prime Minister Theresa May. for a black-tie dinner with business leaders at Blenheim Palace in London.
During the event,. they reaffirmed their strong alliance and vowed to jointly fight against terrorism and Russian aggression.
They also touched on post-Brexit trade.
But in an interview with Britain's Sun newspaper published late Thursday., America's commander in chief blasted the PM's plans for a business-friendly Brexit saying that that her approach could imperil any future bilateral trade deals.
There are fierce demonstration against the visit. which includes a blimp portraying him as a big baby.
The real-estate mogul turned politician claims he's "fine" with any protests, but then later told The Sun that he felt "unwelcome” in London.