Pope Benedict XVI and four Roman Catholic bishops in Kentucky asked the US state's governor to commute the death sentence of an inmate set to be executed on September 16.
Archbishop Joseph E. Kurtz of Louisville presented Governor Steve Beshear with a letter written on the Pope's behalf by Archbishop Pietro Sambi, the papal nuncio to the United States.
It asks that 53-year-old Gregory L. Wilson not be executed because of questions about Wilson's mental status.
Mr Beshear responded with a statement saying he believes capital punishment is appropriate for some crimes and that he found no circumstances for setting aside the sentence after conducting an "exhaustive review" of Wilson's case.
Mr Beshear said he pledged to review clemency petitions for Wilson after final court appeals are complete.