House Oversight and Government Reform Committee Chairman Trey Gowdy (R-SC) questions Deputy Assistant FBI Director Peter Strzok during ajoint hearing of his committee and the House Judiciary Committee in the Rayburn House Office Building on Capitol Hill July 12, 2018 in Washington, DC.

Former Republican congressman Trey Gowdy has joined President Donald Trump's legal team amid a fast-moving impeachment inquiry in the House — but he won't be able to start until next year, Trump said Thursday.

The president, speaking to reporters outside the White House before traveling to Minneapolis for a campaign rally, said that federal lobbying rules prevent Gowdy from working as Trump's outside counsel until January.

"Trey Gowdy is a terrific guy. I think there's a problem with, he can't start for another couple of months because of lobbying rules and regulations. So you'll have to ask about that," Trump said.

The South Carolina Republican joined white-collar law firm Nelson Mullins Riley & Scarborough after he left Congress in 2018.

Gowdy had been a Fox News contributor since January — but he was fired from that role, a network spokesperson confirmed to CNBC on Wednesday, before Trump's lawyer Jay Sekulow announced the new addition to the legal team.

A source familiar with the situation told CNBC on Wednesday that Gowdy representing the president would pose a conflict of interest with his role as a Fox contributor.

"I have known Trey for years and worked with him when he served in Congress," Sekulow said in a statement Wednesday. "His legal skills and his advocacy will serve the president well. Trey's command of the law is well known and his service on Capitol Hill will be a great asset as a member of our team."

But The New York Times' Maggie Haberman said Trump's comments suggest Gowdy "is unlikely to ever join in the capacity he was hired for."

"Someone in West Wing badly wanted a win internally and put out Gowdy before it was a done deal. So it was quickly done yesterday and then had to be undone," Haberman tweeted.

Haberman TWEET

Neither Gowdy nor Sekulow immediately responded to CNBC's requests for comment on Trump's most recent remarks.

Gowdy told The Greenville News at the start of 2019 that he had no plans to return to politics as an elected official or as a lobbyist.

The impeachment inquiry centers around Trump's July 25 call with Ukraine President Volodymyr Zelensky, in which the U.S. president asked for Ukraine to "look into" unsubstantiated corruption allegations against former Vice President Joe Biden — Trump's possible 2020 rival — and his son Hunter. Trump also asked Zelensky to "do us a favor though" and investigate Ukraine's connection to former special counsel Robert Mueller's Russia probe.