Sen. Al Franken, D-Minn., said Monday he still does not recall sexually harassing and assaulting four women who have made allegations against him, but promised at the same time that he would work harder to make sure it doesn't happen again.

He said in the case of radio host Leeann Tweeden, he remembers being on a USO tour with her in 2006, but doesn't remember forcing her to kiss him as they rehearsed a skit. He said he apologized for that incident because he respects her memory of what happened, even though he doesn't remember it that way.

"I said that I recall that differently from Leeanne, but I feel that you have to respect women's experience," Franken told reporters outside his Senate office in a five-minute press conference.

He also said of the other incidents alleged by women: "Those are instances that I do not remember."

Franken reiterated his earlier statements over the last week by apologizing not for the incidents alleged by these women, but for how they feel about it.

"From these stories, it's been clear that there are some women, and one is too many, who feel that I've done something disrespectful and that's hurt them, and for that I'm tremendously sorry," he said.

At the same time, Franken seemed to acknowledge that something must have happened, because he said he would work to make sure it doesn't happen again.

"And I know that I am going to have to be much more conscious when in these circumstances, much more careful, much more sensitive, and that this will not happen again going forward," he said.

"I'm going to try to learn from my mistakes, and in doing so, I've been doing a lot of reflecting, and I want to be someone who adds something to this conversation," Franken added.

"If you had asked me two weeks ago, would any woman come forward with an allegation like this, I would have said no. So I cannot speculate," Franken said when asked if other women would be making allegations of assault against him.

"This has been a shock and it has been extremely humbling. I am embarrassed. I feel ashamed. What I'm going to do is I'm going to start my job and go back to work," Franken said.

Franken said he expects the Senate Ethics Committee to carry out a full investigation into the charges against him, and said he would be "open" to allowing that committee to release its full report.