Republican presidential candidate and former New Jersey Gov. Chris Christie laid into former President Donald Trump Wednesday, calling him "juvenile" and a "baby" after the latter targeted him with fat jokes.

"Look, he's a juvenile. He's a baby. Only children talk like that. He never said that about me when he offered me White House Chief of Staff," Christie told Fox News' Bret Baier during an appearance on "Special Report."

"He never said that about me when he offered me Secretary of Homeland Security, twice. Never said that about me when he offered me Secretary of Labor. I wasn't any of those things then," he said.

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"Look, the minute you speak out against him, Bret, you know what he does? He lashes back out like a child. And if you or I were raising that child, we'd send them to their room, not to the White House," he added.

Following the official launch of Christie's second presidential campaign Tuesday, Trump made multiple social media posts that appeared to mock the former governor's weight.

"How many times did Chris Christie use the word SMALL? Does he have a psychological problem with SIZE?" Trump wrote on Truth Social. 

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"Actually, his speech was SMALL, and not very good. It rambled all over the place, and nobody had a clue of what he was talking about. Hard to watch, boring, but that’s what you get from a failed Governor (New Jersey) who left office with a 7% approval rating and then got run out of New Hampshire. This time, it won’t be any different!" he added.

Trump later posted a doctored video of Christie's announcement speech with what appeared to be a buffet of food in front of him. The doctored video also made Christie look as if he was holding a plate full of food.

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Fox reached out to Trump's campaign for comment but did not immediately receive a response.