FBI Director James Comey on Wednesday defended his decision to tell Congress that he was reopening the investigation into Hillary Clinton's emails with less than two weeks before Election Day, and said not telling Congress would have been a big mistake.

"Concealing, in my view, would be catastrophic," Comey told the Senate Judiciary Committee.

At the same, Comey admitted he was worried his decision may have affected the election.

"It makes me mildly nauseous to think we might have had some impact on the election," he told Sen. Dianne Feinstein, D-Calif.

Comey sent a letter to Congress on Oct. 28 notifying lawmakers that the FBI was going to renew its investigation into Clinton's emails after they found "thousands" of those emails during an unrelated investigation into Anthony Weiner.

Comey told the Senate panel on Wednesday that he had two bad choices: "Either announce restarting the Clinton investigation or concealing it."

Despite the blowback, Comey says he has no regrets in telling Congress so close to Election Day.

"Even in hindsight, and this has been one of the world's most painful experiences, I would make the same decision," he said.

On Tuesday Clinton again blamed Comey for her loss to Trump, and said if the election were held about a week earlier, she would have won.