The Supreme Court has allowed the US state of Missouri to proceed with its plan to execute death row inmate Marcellus Williams, rejecting a last-ditch request to intervene on his behalf.

The justices rejected two separate appeals to spare Williams’ life, over the objection of the three liberal justices.

Williams’ execution by lethal injection is scheduled for Tuesday evening.

Joseph Amrine, who was exonerated two decades ago after spending years on death row, speaks at a rally to support Missouri death row inmates Marcellus Williams
Joseph Amrine, who was exonerated two decades ago after spending years on death row, speaks at a rally to support Missouri death row inmates Marcellus Williams (Jim Salter/AP)

The high court’s decision came a day after the Missouri Supreme Court and Republican governor Mike Parson declined to step in on Williams’ behalf.

Williams, 55, has long maintained that he is innocent in the 1998 killing of social worker Lisha Gayle, who was repeatedly stabbed during a burglary of her suburban St Louis home.

His execution is opposed by Ms Gayle’s family and the prosecutor’s office that put Williams on death row.

Missouri’s Republican attorney general, though, has pushed for the execution to happen.

The execution is opposed both by Ms Gayle’s family and the prosecutor’s office that put Williams on death row — an unprecedented combination.

“The family defines closure as Marcellus being allowed to live,” the clemency petition stated. “Marcellus’ execution is not necessary.”

Williams is among inmates in five states who are scheduled to be executed in the span of a week — an unusually high number that defies a years-long decline in the use and support of the death penalty in the US.

The first was carried out on Friday in South Carolina.

The others are scheduled to take place in Texas on Tuesday, and in Oklahoma and Alabama on Thursday.