Watch: Fox anchor Chris Wallace makes his own news with move to CNN

Veteran anchor Chris Wallace has left Fox News after 18 years for CNN, dealing a significant blow to Fox's news operation at a time that it has been overshadowed by the network's opinion side.

Wallace delivered the surprising news that he was leaving at the end of the "Fox News Sunday" show he moderates, and within two hours CNN announced he was joining its new streaming service as an anchor. CNN+ is expected to debut in early 2022.

"It is the last time, and I say this with real sadness, we will meet like this," Wallace, who is 74, said on his show, which airs on the Fox network and is later rerun on Fox News Channel. "Eighteen years ago, the bosses here at Fox promised me they would never interfere with a guest I booked or a question I asked. And they kept that promise."

Wallace was a veteran broadcast network newsman, working at both ABC and NBC News, before the late Roger Ailes lured him to Fox with the promise of his own Sunday show. Methodical and never showy — in contrast to his father Mike, the legendary "60 Minutes" reporter — Chris Wallace was known for his willingness to ask hard questions of all guests no matter their politics.

He was the first Fox News personality to moderate a presidential debate, doing it in 2016 and 2020. The debate he moderated last year went off the rails when then-President Donald Trump repeatedly interrupted Democratic challenger Joe Biden.

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Wallace generally co-existed with Fox's opinion side and infrequently took them on publicly, although in 2017 he said it was "bad form" when opinion hosts bashed the media.

But he had grown privately frustrated with the overall tenor at Fox, where conservative opinion hosts have been elevated and amplified, particularly after the network's ratings took a brief hit following the 2020 election. The network ousted two news executives involved in the controversial — but correct — Election Night declaration that Biden had won in Arizona, a call that infuriated Republican Trump.

His track record had given Wallace a large measure of independence at Fox, despite the network's overall tilt. "I have been free to report to the best of my ability, to cover the stories I think are important, to hold our country's leaders to account," he said on Sunday. "It's been a great ride."

His announcement came as a surprise; even guests on his show Sunday hadn't been tipped off they were seeing his finale.