In a White House interview, Trump said he had a friendship with the two men, but described Johnson as "the right man for the time."
Asked which UK leader he supported, Mr Trump said, "I like them both. I think Boris will get it right. They're both friends of mine. What I'd like to see is for Nigel and Boris to come together. I think that's a possibility."
Trump stressed the need for a systematic separation between London and the EU to facilitate continued trade between Britain and the United States.
The Nigel Farage, has said earlier that he will not run in elections scheduled for next month and prefer to call for the rejection of the agreement reached by Johnson to exit the country from the Union.