DULUTH, Minn. — A priest recently tapped by Pope Francis to become a bishop for a northern Minnesota diocese has resigned after an allegation of sexual abuse of a minor in the 1980s surfaced before he could take up his post.

The Vatican announced Monday that Francis had accepted the resignation of Bishop-elect Michel Mulloy, whom the pope named in June to head the Duluth diocese. Mulloy was supposed to be elevated to bishop’s rank in an Oct. 1 ceremony in Duluth. The Vatican did not provide details.

At the time of his appointment, Mulloy was serving as diocesan administrator in Rapid City, S.D. The Diocese of Rapid City said in a statement that it received the allegation last month and that it dates back to the 1980s. It said there have been no additional allegations of abuse involving Mulloy.

The Associated Press left a message seeking comment Monday at Mulloy’s office in the Rapid City diocese.

It is highly unusual for a priest who has been selected to be a bishop to resign before that can happen. But the development underlines the pontiff’s oft-stated resolve to crack down on predator priests as well as insist that any allegation of sexual abuse be promptly investigated.