An "embarrassed" and "ashamed" Sen. Al Franken, D-Minn., apologized to supporters and the women who say he groped them in a brief appearance on Monday outside his office on his first day back in the Senate since the accusations became public.

"I just want to again say I am sorry. I know there are no magic words I can say to regain your trust, I know that's going to take time," he said. "I hope that starting work today I can do that."

Franken told reporters he did not know if more allegations would surface.

"If you had asked me two weeks ago if any woman would come forward with any allegation like this, I would have said no," the senator said. "I cannot speculate."

He continued: "This has been a shock, and it's been extremely humbling. I am embarrassed. I feel ashamed. What I'm going to do is I'm going to start my job, I'm going (to) go back to work, I'm going to work as hard as I can."

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Facing a slew of cameras and reporters who asked him about the allegations and upcoming Senate ethics inquiry, Franken said that he did not recall the latest allegations in which women say the senator groped them during photos.

"I'm going to try and learn from my mistakes," he said, vowing to be "much more sensitive" in his dealings with women. "This will not happen again going forward."

Franken also said he couldn't address what the standard should be for someone to resign but added that he was trying to move forward and regain voters' trust.

The senator has been accused of misconduct by four women, including radio host Leeann Tweeden, who said earlier this month that Franken "kissed and groped" her without consent on a 2006 USO tour, releasing a photo showing Franken groping her breasts over body armor while she was asleep. A second woman, Lindsay Menz, told CNN she was groped in 2010 while taking a photo with the senator at the Minnesota State Fair. The third and fourth allegations of similar groping during political events were made anonymously to the Huffington Post.

Franken apologized directly to Tweeden. He said Monday he does not recall the incidents with the other accusers. In a statement to the Huffington Post, which had reported that one woman said Franken suggested he go to the bathroom with her after putting his hand on her buttocks, Franken said he never propositioned anyone to join him in the bathroom.

While Trump tweeted about the photo of Tweeden and Franken earlier this month, dubbing the senator "Al Frankenstien," he has not called on the senator to take any direct action. The White House declined to weigh in Monday afternoon.

"The president’s not going to weigh in on every single matter on this. Every single day we’ve got people from the media, from Hollywood, from members of Congress that have allegations brought against them, and we think that this should go through due process," Press Secretary Sarah Huckabee Sanders said, dodging questions about "Access Hollywood" audio unearthed during the campaign in which a nearly 60-year-old Trump could be heard bragging that being famous allows men to grope women.

The New York Times reported over the weekend that Trump has questioned the authenticity of that audio, though in the aftermath of its release, he acknowledged that it was him on the tape and issued a rare apology.

"This was litigated and answered during the election by the overwhelming support for the president and fact that he's sitting here in Oval Office today," Sanders said.