The Midwestern US state of Missouri said Friday that it was suspending its next execution amid a controversy over the drug used for lethal injections.

"I have directed the Department of Corrections that the execution of Allen Nicklasson, as set for October 23, will not proceed," Governor Jay Nixon said.

Almost every state that practices the death penalty has adopted the barbiturate pentobarbital for lethal injections.

But as supplies dwindle, states that practice capital punishment are turning to new drugs or new providers, though not without hiccups.

Missouri had planned to use propofol -- the anesthetic that killed Michael Jackson -- to put Nicklasson to death.

It was forced to return its stocks, however, when the German manufacturer refused to allow the drug to be used for human executions.

Nixon said he was suspending the execution "in light of the issues that have been raised surrounding the use of propofol in executions."

The governor said a new execution date will be set for Nicklasson. He has not specified what will become of another lethal injection scheduled for November 20.

According to local media, elected officials in Missouri have proposed building a new gas chamber, a practice that was discontinued in 1965.

Most other US states that practice capital punishment have turned to compounding pharmacies to customize their supply of lethal injection drugs.

The substances, however, have not been approved by federal regulators, eliciting multiple lawsuits from death row inmates who say the could die in excruciating pain as a result.

Missouri has executed 68 prisoners since the death penalty was reestablished in the United States in 1976. Its last execution was on February 9, 2011.