Washington (CNN) Sen. Susan Collins said she is "appalled" by a tweet from President Donald Trump disparaging the woman who has accused Supreme Court nominee Brett Kavanaugh of sexual assault.

The Maine Republican called the statement from the President "inappropriate and wrong."

"I was appalled by the President's tweet," Collins said Friday, according to audio obtained by CNN of an event where she spoke with local reporters.

The senator, who is a crucial swing vote on Kavanaugh's nomination, was responding to a question on what she thought of a tweet from the President suggesting that Christine Blasey Ford should have come forward with her allegation against Kavanaugh earlier.

"We know that allegations of sexual assault -- I'm not saying that's what happened in this case -- but we know that allegations of sexual assault are one of the most unreported crimes that exist, so I thought that the President's tweet was completely inappropriate and wrong," Collins said.

On Friday, Trump escalated his criticism of Ford, who has alleged that Kavanaugh sexually assaulted her at a party in the early 1980s when they were in high school. Kavanaugh has categorically denied the allegations.

After tweeting on Friday morning that Kavanaugh is "a fine man," Trump cast doubt on Ford's credibility, saying in a tweet that "if the attack on Dr. Ford was as bad as she says," charges would have been filed. In a later tweet, Trump said, "Why didn't someone call the FBI 36 years ago?"

According to the Portland Press Herald, which first reported on the comments from Collins, the senator was at an event in Portland, Maine, when she weighed in on the President's tweets.

Senate Republicans are negotiating with Ford's lawyers to determine the terms under which she would be willing to testify before the Senate Judiciary Committee, which handles Supreme Court nominations, about her allegations next week.

"I think we should try to accommodate Professor Ford within the realm of reasonableness," Collins said. "I do think that both she and Judge Kavanaugh need to testify under oath, but I believe we should attempt to make this as comfortable a process for her as possible."

Collins said that Monday would be the "preferred date" for a hearing but she didn't "see a problem" with the possibility of it taking place Wednesday or Thursday.