THOSE are fighting words!” That’s what a stunned MATT LAUER told pals after his former “Today” co-host KATIE COURIC blasted the NBC show for being “stale” and “soft,” say sources.

“It’s all-out war between Matt and Katie!” declared an insider.

“Matt is extremely thin-skinned when it comes to any criticism of ‘Today,’ and he feels Katie has stabbed him in the back.

“Even though Katie didn’t criticize him directly for the show losing steam, he still took her comments as a blow to the gut.”

Matt, who recently signed a new $21.5 million “Today” contract, feels Katie took a cheap shot at the show because she’s now a special correspondent for rival network ABC News, explained the source.

Even worse, ABC’s “Good Morning America” has been beating “Today” in the ratings since knocking it out of the top spot when Katie, 55, substituted as a co-anchor in April.

Katie rubbed salt in the wound when she boasted in a recent interview that during her 15-year stint on “Today,” the show “would always be doing a little something new and fresh. It doesn’t seem that way anymore…Also, there was much more hard news.”

Katie now hosts her own daytime talk show, and after supporting her for years through personal and professional challenges, “Matt feels utterly betrayed,” said the source.

“Since they parted ways as ‘Today’ colleagues, Matt, Katie and their families have socialized together, especially over the holidays. But don’t look for that to happen this year.

“Hell is more likely to freeze over.”