Jefferson City, Missouri - Missouri Governor Mike Parson has rejected calls for clemency including an appeal from the pope in the high-profile case of a death row inmate and said his execution is to proceed as planned.

"Today, Governor Mike Parson confirmed that the state of Missouri will carry out the sentence of Mr. Ernest Lee Johnson on Tuesday, October 5, 2021, as ordered by the Supreme Court of Missouri," Parson's office said in a statement issued Monday in the state capital, Jefferson City.

"The state is prepared to deliver justice and carry out the lawful sentence Mr. Johnson received in accordance with the Missouri Supreme Court's order," Governor Parson said.

Johnson is convicted of a triple murder at a general store in Columbia, Missouri, in 1994. His execution has been the subject of protracted legal battles.

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Among those calling for Johnson not to be executed is Pope Francis. The pontiff issued an appeal on October 1, according to the US Death Penalty Information Center.

"Pope Francis sent a letter requesting clemency for #ErnestJohnson to @GovParsonMO this week through the Vatican's ambassador to the U.S.," anti death penalty activist Sister Helen Prejean tweeted.

"The Pope 'wishes to place before you the simple fact of Mr. Johnson's humanity and the sacredness of all human life,'" she added.

Advocates for a stay of execution including former Missouri Supreme Court Judge Michael Wolff argue that Johnson should not have received the death penalty as he is "significantly intellectually disabled," according to the Death Penalty Information Center.

Johnson is to be put to death by lethal injection.