Former House Speaker Newt Gingrich posted a video apology Thursday after President-elect Donald Trump subtly rebuked him for saying he had softened on his promise to "drain the swamp."

"I want to report that I made a big boo boo," Gingrich said at the outset of his video apology. "I talked this morning with President-elect Donald Trump and he reminded me that he likes draining the swamp, I mischaracterized it the other day."

"He intends to drain the swamp," Gingrich continued. "He describes it as 'DTS.' He thinks taking on Boeing in price is an example of draining the swamp."

Gingrich, who was a fierce Trump supporter throughout the 2016 campaign, said in a Wednesday interview that Trump had softened on the phrase and no longer wanted to use it. But the president-elect pushed back on Thursday in a strongly worded tweet.

"I want all of you to know, I goofed," Gingrich said. "Draining the swamp is in, the alligator should be worried, and you'll hear me write more about alligators and the swamp."

Gingrich concluded: "I thought I owed it to all the folks who follow me, that when I make a mistake, I will be straightforward and tell you: I blew that one. Draining the swamp is in, President-elect Trump wants to do it, and you're going to get to be part of it."

"Draining the swamp" was the go-to phrase Trump used toward the end of his presidential campaign. The message was used as a promise to rid government of lobbyists and special interests.

In recent weeks, some critics have begun to doubt how sincere Trump was about his message, as the president-elect appoints individuals who come from places like Goldman Sachs.