Reuters quoted Mr Clark as saying that Texas was confident it would be able to continue with the deaths, despite the shortage.

Richard Dieter, who heads the Washington-based Death Penalty Information Center, said other states would be having similar problems.

“The states really scramble to go all over to get drugs,” he told AP.

“Some went overseas, some got from each other. But these manufacturers – a number them are based in Europe – don’t want to participate in our executions. So they’ve clamped down as much as they can.”