Oklahoma Gov. Mary Fallin postponed an inmate's scheduled execution Wednesday, saying a drug that the state Department of Corrections had received to carry out a lethal injection didn't match those listed in the agency's protocols.

Fallin said prison officials received potassium acetate for use in Richard Glossip's execution, but Oklahoma's guidelines call for the use of potassium chloride. She reset Glossip's execution for Nov. 6, saying it would give the state enough time to determine whether potassium acetate is a suitable substitute, or to find a supply of potassium chloride.

It's not clear why the error wasn't caught before Wednesday, or announced until an hour after Glossip's scheduled execution.

Part of Wednesday's delay, though, occurred as the Corrections Department waited for the U.S. Supreme Court to weigh in on Glossip's claim of innocence. Justices ultimately rejected his appeal.

Glossip was convicted of ordering the 1997 killing of Barry Van Treese, who owned the Oklahoma City motel that Glossip managed.

Glossip has long claimed he was framed by hotel handyman Justin Sneed, who admitted to fatally beating Van Treese with a baseball bat, but said he did so only after Glossip promised him $10,000. Sneed — who is serving a life sentence — was the state's key witness against Glossip in two separate trials.

Glossip was originally scheduled for execution on Sept. 16. But just hours earlier, the Oklahoma Court of Criminal Appeals granted a rare two-week reprieve to review his claims of new evidence, including another inmate's assertion that he overheard Sneed admit to framing Glossip.

But in a 3-2 decision Monday, the same court denied Glossip's request for an evidentiary hearing and emergency stay of execution, paving the way for his execution to proceed. The court majority wrote that the new evidence simply expands on theories raised in his original appeals.

On Tuesday, Glossip's attorneys made a last-ditch request to the U.S. Supreme Court.

"Recently discovered evidence demonstrates substantial doubt about Sneed's credibility," his attorneys wrote in a petition to the court.

Attorney General Scott Pruitt urged the high court to not stop the execution, arguing that another delay for Glossip would amount to a "travesty of justice."

Gov. Mary Fallin has repeatedly denied Glossip's request for a 60-day stay of execution. In a statement Tuesday, the Republican said she still had no plans to stop the punishment.

"The state of Oklahoma has gone to extraordinary lengths to guarantee that Richard Glossip is treated fairly and that the claims made by him and his attorneys are taken seriously," Fallin said. "He has now had multiple trials, seventeen years of appeals, and three stays of his execution. Over and over again, courts have rejected his arguments and the information he has presented to support them."

A representative for Pope Francis asked Fallin to commute Glossip's death sentence, saying a commutation "would give clearer witness to the value and dignity of every person's life." The letter from Archbishop Carlo Maria Vigano is dated Sept. 19, but was released Wednesday by the governor's office.

A spokesman for Fallin said the governor doesn't have the authority to grant a commutation.

Glossip also is the lead plaintiff in a separate case challenging the state's three-drug execution protocol. His attorneys argue that the sedative midazolam wouldn't adequately render an inmate unconscious before the second and third drugs were administered. They said that presented a substantial risk of violating the Eighth Amendment's prohibition on cruel and unusual punishment.

However, the U.S. Supreme Court voted 5-4 in June that the sedative's use was constitutional.

Oklahoma first used midazolam last year in the execution of Clayton Lockett, who writhed on the gurney, moaned and clenched his teeth for several minutes before prison officials tried to halt the process. He died 43 minutes after the sedative was first injected.

The state then increased by five times the amount of midazolam it uses and executed Charles Warner in January. He complained of a burning sensation but showed no other obvious signs of physical distress.

Oklahoma has two more executions planned in upcoming weeks. Benjamin Cole is set to be executed on Oct. 7 for the 2002 killing of his 9-month-old daughter, and John Grant is scheduled to die on Oct. 28 for the 1998 stabbing death of a prison worker at the Dick Connor Correctional Center in Hominy.