President Donald Trump issued a vague threat to an unnamed Democratic senator during a Monday press conference, saying he had "seen that person in very bad situations."

Trump was questioning Senate Judiciary Committee members' interest in his Supreme Court nominee Brett Kavanaugh's drinking habits while investigating decades-old sexual-misconduct allegations.

When pressed to clarify his comment, Trump refused, joking he would "save it for a book like everybody else."

President Donald Trump issued a vague threat to an unnamed Democratic senator during a Monday press conference while addressing scrutiny of his Supreme Court nominee Brett Kavanaugh's drinking habits.

Trump was fielding questions from reporters about an FBI investigation into sexual-misconduct allegations when he said he supported Kavanaugh being interviewed. But he cast doubt on Senate Democrats' apparent interest in the judge's drinking habits in high school and college.

"They're going back to high school, they're saying he drank a lot one evening in high school," Trump said, referring to the Senate Judiciary Committee's questions into Kavanaugh's past drinking habits after two women described drunken incidents of sexual assault and misconduct from his time in high school and college that Kavanaugh denied.

Trump continued: "I happen to know some United States senators, one on the other side who is pretty aggressive — I've seen that person in very bad situations ... somewhat compromising."

Trump then added that though he thought it was "very unfair to bring up things like this," he left responsibility for the scope of the investigation to "whatever the senators want."

Trump's comments come after a weekend of mixed messages for the FBI's additional background check on Kavanaugh that Trump approved Friday afternoon. Experts and lawmakers have spoken out on the investigation's apparently limited scope and time allowance, though Trump said Sunday investigators had "free rein."

When later pressed to elaborate on the comment about catching senators in "compromising" situations, Trump told the reporter that he would "save it for a book like everybody else."

"I'm not giving it to you," he said.