Livingston, Texas - A Texas man is to be executed by lethal injection on Wednesday for the 2011 murder of a pastor that he insists he did not commit.

Steven Nelson (37) has spent more than a dozen years on death row for the murder of Clint Dobson (28) during a robbery of the NorthPointe Baptist Church in Arlington, near Dallas.

Dobson was beaten and suffocated with a plastic bag. Judy Elliott, the church secretary, was also badly beaten but survived.

Nelson's appeals against his conviction and death sentence have been repeatedly rejected by Texas courts, and the US Supreme Court has declined to hear his case.

Nelson was interviewed by AFP recently at the maximum-security prison in Livingston, a town 75 miles north of Houston, where he is awaiting his execution.

"It's hard at times," he said. "You're waiting to be put to death. So that kind of breaks a little part of you every day... You just don't want to do nothing."

Nelson acknowledges that he served as a lookout during the robbery and that he entered the church after the murder to steal some items. But he says it was his two accomplices, who were never brought to trial, who committed the murder.

"I didn't know what was going on on the inside," he said, claiming his friends "blamed everything on me."

"So they're free and I'm locked up," he said. "I'm here on death row because of what somebody else did."

"I'm an innocent man," Nelson said. "I'm being executed for a crime, a murder, that I did not commit."

Nelson married a French woman, Helene Noa Dubois, while in prison. He said it is up to her to decide whether she wants to witness his execution, although he does not want her to be there.

"I really don't want her to see that – me getting pumped full of drugs and being overdosed with drugs to kill me, to make my heart stop."

"But if she makes that choice to be there then that's her choice."

There were 25 executions in the US last year, and there has been one so far this year, in South Carolina.

The death penalty has been abolished in 23 of 50 states, while three others – California, Oregon, and Pennsylvania – have moratoriums in place. Three states – Arizona, Ohio, and Tennessee – that had paused executions have recently announced plans to resume them.

President Donald Trump is a proponent of capital punishment and on his first day in the White House he called for an expansion of its use "for the vilest crimes."