Ken Starr, the independent counsel charged with investigating former President Bill Clinton, said Sunday that President Trump's disputed denial that he has never considered firing special counsel Robert Mueller was "absolutely" grounds for impeachment.

"I think lying to the American people is a serious issue that has to be explored. I take lying to the American people very, very seriously. So, absolutely," Starr told ABC.

"I think that is something that Bob Mueller should look at," he added.

Starr wrote the Starr Report in 1998 that alleged Clinton lied about an extramarital affair with then-White House intern Monica Lewinsky during sworn testimony. He said he thinks Trump has "extremely broad" power to dismiss people like former FBI Director James Comey or Mueller.

"I have a very different perspective and a much more robust view of presidential power than many of the folks who have been speaking to this," Starr said of possible obstruction of justice charges.

"But, that having been said, it would have been extremely unwise. It would have been Armageddon."