The governor of California, Arnold Schwarzenegger, has refused to grant clemency to a killer who asked to be spared because of his age and frailty.
Allen's lawyers say it would be cruel to kill him because of his infirmity
Clarence Ray Allen, who is legally blind and uses a wheelchair, is now set to die by lethal injection on Tuesday, the day after his 76th birthday.
He has spent 23 years on death row for ordering the murder of three people.
Mr Schwarzenegger last month sparked anger when he denied former gang leader Stanley "Tookie" Williams clemency.
The governor's latest ruling means that barring a last-minute reprieve by the courts, Allen will be executed as scheduled at San Quentin prison.
His lawyer said Allen, who is also partially deaf, had ordered a "hefty" last meal and was looking forward to a birthday visit by his grandchildren on Monday.
California's oldest death row resident had appealed to Mr Schwarzenegger for a reprieve on the grounds he was too aged and infirm to execute.
But, in a written statement, the governor said his crimes were too serious for life imprisonment to be appropriate.
While already behind bars serving life for murder, Allen ordered the killing by hitmen of three witnesses whose testimony helped convict him.
Allen ordered the killing of three witnesses who helped convict him
Mr Schwarzenegger said: "Allen's crimes are the most dangerous sort because they attack the justice system itself. The passage of time does not excuse Allen from the jury's punishment."
His lawyers have appealed to the US Supreme Court to stay his execution on the grounds that it would be cruel and unusual punishment because of his infirmity.
Anti-death penalty campaigners have also rallied on his behalf, although his case has not seen the kind of celebrity support shown for Williams last month.
Williams, who co-founded the Crips, one of the world's biggest and deadliest gangs, was executed by lethal injection on 13 December.
Celebrities and civil rights groups argued his sentence should be commuted to life because he had spent years in prison campaigning against gang violence.