The US Supreme Court has been asked to block the execution of a Texas man who claimed he drank the blood of his young victim.

Pablo Lucio Vasquez, 38, is due to be executed by lethal injection after 6pm on Wednesday evening (CDT) for the murder of 12-year-old David Cardenas in 1998.

His execution would be the 11th this year in the US and the sixth in Texas.

But Vasquez’s lawyer James Keegan says several potential jurors in the murder trial may have been improperly excused because they were either against the death penalty or not comfortable imposing such a judgement.

Mr Keegan has appealed to the Supreme Court for a reprieve so his claims can be reviewed.

But state lawyers oppose the move.

Assistant Texas Attorney General Jeremy Greenwell said that any exclusion of potential jury members was legally proper, adding that the latest appeal is “nothing more than a meritless attempt to postpone (Vasquez’s) execution”.

The appeal is the latest in a number of attempts to save Vasquez.

The most recent was a month ago and asserted that Vasquez was mentally ill and, therefore, should not be able to be sentenced to death.

David Cardenas had been a friend of Vasquez’s cousin Andres Rafael Chapa and both boys had been at a party in the Texas border town of Donna with Vasquez and others on 18 April, 1998.

Vasquez told police he was drunk and high when voices told him to kill seventh-grader David, beating him with a pipe and then slitting his throat, saying that the devil had told him to “take (the head) away from him”.

He said Chapa had used a shovel in an attempt to help. Chapa pleaded guilty to murder and is serving a 35-year jail term.

Vasquez told detectives that he had later lifted David’s body, allowing the blood to drip on his face before drinking it, adding in a statement: “Something just told me to drink”.

David’s body was found missing limbs and nearly decapitated in a vacant field five days after the murder.

Joseph Orendain, the lead trial prosecutor, described the case as “really horrendous”, adding: “Did he drink (the blood)? I don’t know.”