Gingrich: A president 'cannot obstruct justice'

Former House Speaker Newt Gingrich (R-Ga.), a staunch supporter of President Trump, said Friday that a "president cannot obstruct justice."

Gingrich said that as president, Trump was well within his authority to fire the head of the FBI.

“The president of the United States is the chief executive officer of the United States. If he wants to fire the FBI director, all he has to do is fire him,” said Gingrich in comments at the National Press Club, where he was promoting a new book.

His comments sparked pushback on Twitter, with many noting that Gingrich had voted to impeach former President Bill ClintonBill ClintonGOP rep: North Korea wants Iran-type nuclear deal Lawmakers, pick up the ball on health care and reform Medicaid The art of the small deal MORE, including an article that charged him with obstruction of justice.

Gingrich's comments came after Trump in a tweet earlier this morning said that he was being investigated for firing former FBI Director James Comey.

"I am being investigated for firing the FBI Director by the man who told me to fire the FBI Director! Witch Hunt," the president tweeted.

It was unclear what information the president was using to make the claim. Trump was also likely referring to Deputy Attorney General Rod Rosenstein, who penned a memo last month questioning Comey's handling of the probe into Hillary ClintonHillary Diane Rodham ClintonBiden slams Trump over golf gif hitting Clinton Overnight Cybersecurity: Equifax hit by earlier hack | What to know about Kaspersky controversy | Officials review EU-US privacy pact Overnight Tech: Equifax hit by earlier undisclosed hack | Facebook takes heat over Russian ads | Alt-right Twitter rival may lose domain MORE's use of a private email server while secretary of State.

The White House initially used that memo to justify Trump's decision to fire Comey.

Rosenstein also tapped former FBI Director Robert Mueller to be special counsel and oversee the probe into Russian meddling in the 2016 election, including any ties between the Trump campaign and Moscow.

Reports earlier this week said that probe was being expanded to cover whether Trump obstructed justice by firing Comey.

Comey testified before Congress last week that the president had asked him to drop a probe into former national security adviser Michael Flynn, before his firing, and called the Russia probe a "cloud" over his administration.

Gingrich slammed Mueller, accusing him of packing his team with Trump opponents.

”Mueller is surrounding himself with people that are conducting a witch hunt," said Gingrich.

The former Speaker on Friday was touting his new book, "Understanding Trump."