Retiring U.S. Sen. Roy Blunt said he will not vote in the affirmative for U.S. Supreme Court nominee Ketanji Brown Jackson, while acknowledging her confirmation is all but assured.

Blunt, 72, has represented Missouri in Congress's upper chamber since 2011 and will leave office in January.

"There are two criteria I set: is the person qualified for the job and the nominee's judicial philosophy. She's certainly qualified, has a great personality and will be a good colleague on the Court," Blunt told ABC's "This Week" program Sunday.

"Her judicial philosophy seems to be not the philosophy at looking at what the law and the Constitution say and applying that, but using some method to look at the Constitution as a more flexible document, and there are cases showing that's her view."

Blunt told "This Week" moderator George Stephanopoulos it is clear Jackson will become the first Black woman to sit on the nation's highest court.

"I think she certainly will be confirmed and I think it'll be a high point for the country to see her take her unique perspective on the Court, but I don't think she's the kind of judge who will do the kind of work I think needs to be done," Blunt said. "I won't be supporting her but I'll be joining others in understanding the importance of this moment."

As of presstime, one Republican senator, Maine's Susan Collins, is on record saying she will vote to confirm Jackson.