WATCH: Fox News' John Roberts belatedly calls out Trump for 'unfair' attacks on CNN and NBC

After taking criticism for not speaking out at President Donald Trump's attacks on CNN Friday, Fox News reporter John Roberts belatedly called out Trump for attacking rival networks as "fake news."

During a news conference with United Kingdom Prime Minister Theresa May, Trump refused to take a question from a CNN reporter on the grounds that the network was filled with “fake news.”

Trump then decided to call on a reporter from what he described as a “real network” — Fox News White House reporter John Roberts. Instead of sticking up for his fellow journalists, Roberts continued to ask his question as though nothing had happened.

Later on Friday, Roberts went on the air to try to make amends for his silence on the president's attacks.

"The president called out one of my colleagues, Kristen Welker of NBC News, as dishonest, he said NBC News was dishonest," he said. "He also called out CNN as not a real network, fake news. Let me just add that I know Kristen Welker, she's as honest as the day is long, to call her dishonest is unfair. I used to work at CNN, they have fine journalists there who risk their lives to cover the news around the world. And to say they're not a real network, or fake news, is also unfair."

Watch the video below.