UPDATE, 1:21 P.M. ET: Fox News Chief White House Correspondent John Roberts released a statement reacting to the president's exchanges with NBC's Welker and CNN's Acosta. Read it below.

During President Trump’s joint press conference with British Prime Minister Theresa May on Friday, CNN’s hostile White House Correspondent Jim Acosta demanded to ask a question. As Trump refused and dismissed CNN as “fake news,” he turned to John Roberts of Fox News, remarking, “Let’s go to a real network.” A dejected Acosta muttered in response: “Well, we’re a real network too, sir.”

As the president prepared to take another question, Acosta shouted off mic: “Mr. President, since you attacked CNN, can I ask you a question?” As Trump called on Roberts, Acosta interrupted: “Can I ask you a question?” Trump hit back: “No, no. John Roberts, go ahead. CNN’s fake news, I don’t take questions – I don’t take questions from CNN. CNN is fake news, I don’t take questions from CNN. John Roberts of Fox. Let’s go to a real network. John, let’s go – ”

Acosta could then be heard claiming: “Well, we’re a real network, too, sir.”

The “attack on CNN” that Acosta referred to came earlier in the presser, when NBC’s White House Correspondent Kristen Welker asked:

You spent the week taking on NATO allies, criticizing Prime Minister May on her own soil. And I wonder, are you giving Russian President Vladimir Putin the upper hand heading into your talks, given that you are challenging these alliances that he seeks to break up and destroy?

Trump called out the biased question: “See, that’s such dishonest reporting, because – of course, it happens to be NBC, which is possibly worse than CNN, possibly. Possibly.”

UPDATE -- Statement from FNC's John Roberts:

In today's press conference, I paused while my colleague from CNN went back and forth with President Trump over a question. When it became clear that the president wasn't going to entertain a question from him, I proceeded with my question, as did my fellow colleagues in the press corps. I know Kristen Welker of NBC. She is honest as the day is long. For the President to call her dishonest is unfair. I also used to work at CNN. There are some fine journalists who work there and risk their lives to report on stories around the world. To issue a blanket condemnation of the network as "fake news" is also unfair.

Here are excerpts of the two exchanges during the July 13 press conference: