His comments come at a time when British Prime Minister Theresa May is urgently looking to rally enough lawmakers to back her proposed Brexit deal in order to get it through Parliament in two weeks' time. A daunting task given the broad criticism it has received.
Nonetheless, May has repeatedly insisted the terms in which the U.K. is set to leave the bloc at the end of March next year delivers for all of the British people.
When asked about the agreement between Westminster and the EU's other 27 heads of state on Monday, Trump replied: "Sounds like a great deal for the EU."
"I think we have to take a look seriously whether or not the U.K. is allowed to trade because right now if you look at the deal, they may not be able to trade with us," Trump told reporters outside the White House.
"And that wouldn't be a good thing. I don't think they meant that," he added.
In response, Downing Street said it is "very clear" Britain will be in a position to sign trade deals with countries around the world post-Brexit.