In an interview with the British newspaper The Sun, President Donald Trump said that Prime Minister Theresa May’s Brexit “blueprint” for Brexit would likely kill any opportunity for special trade deals with the US.  A critical part of that blueprint would have Great Britain

stick[ing] to a common ­rulebook with Brussels on goods and agricultural produce in a bid to keep customs borders open with the EU.

The EU’s trade rulebook, not just on goods and ag products, but covering all trade, explicitly blocks nations from entering into unilateral trade deals with non-EU nations.  Trade deals with non-EU nations can only be EU trade deals.  Sticking to the EU’s trade rulebook, then, would make it impossible for Great Britain to enter into its own deals with other nations—including with the US.

If they do a deal like that, we would be dealing with the European Union instead of dealing with the UK, so it will probably kill the deal.

If they do that, then their trade deal with the US will probably not be made.

Trump isn’t far wrong on that.

At a joint news conference the day after the Sun interview, though, May said that

the leaders had agreed to pursue an “ambitious” trade deal between the two nations that “works for both countries right across the economies.”

That would seem encouraging for Great Britain, implying as it does that May’s blueprint doesn’t, or will be modified to not, include a commitment to the EU’s trade rulebook.