The pending execution of a Missouri man convicted of murder would constitute torture because he has a medical condition that puts him at risk of painfully choking to death during a lethal injection, human rights groups said Wednesday.

The push to halt the execution by the American Civil Liberties Union and Inter-American Commission on Human Rights comes in the wake of a series of botched executions in the U.S. in recent years.

Russell Bucklew, 49, suffers from a rare health condition that causes large tumors made up of blood vessels to grow on his head, face and neck, which results in severe pain and difficulty breathing.

His execution is currently scheduled for Tuesday.

“This execution should not move forward,” Jamil Dakwar, Director of the ACLU’s Human Rights Program, told Newsweek. “Because the state is pursuing lethal injection, that will most certainly cause severe pain and suffering which under international law is considered torture.”3_15_Death_Penalty_BucklewRussell Bucklew is scheduled to be executed on Tuesday, March 20.MISSOURI DEPARTMENT OF CORRECTIONS

The ACLU wrote a letter to the Inter-American Commission on Human Rights, an international organization headquartered in Washington, D.C., on Wednesday asking that the commission immediately step in to block Bucklew’s execution. There is a substantial risk, the ACLU said, that the lethal injection could cause Bucklew to choke, because of his compromised airway, which would make him suffocate to death in extreme pain. A lethal injection could also cause his tumor to burst, the group added. The commission wrote back the same day to say they had contacted the federal government to again request Bucklew’s execution be delayed until the commission has had time to examine the case.

The office of Missouri Attorney General Josh Hawley did not immediately comment.

The U.S. Supreme Court granted Bucklew a stay in 2014 and ordered a lower court to hear his case, but that court dismissed Bucklew’s challenge to lethal injection.

Bucklew was convicted in state court of first degree murder, kidnapping, burglary and rape, according to court papers, and was sentenced to death for the murder.

Botched executions in multiple states have revived a national debate about the death penalty in recent years. Lethal injection, the method the state plans to use on Bucklew, has the highest rate of failure–over 7 percent–of all methods, according to the Death Penalty Information Center.

Oklahoma will soon resume executions using gas because pharmaceutical companies will no longer sell prisons the drugs needed for lethal injections, according to NBC. A man regained consciousness in Oklahoma during an execution in 2014 because the IV wasn’t placed correctly, NBC reported.

And an Alabama death row inmate is asking that his death sentence be vacated after his attempted execution was “botched and bloody,” according to CNN. The outlet reported that workers tried for over two hours to find a vein in his groin, feet and legs, without success.