Lacking enough of the anesthetic essential to the cocktail of lethal drugs administered during executions, several US states are being forced to postpone the procedure until early next year.

At the heart of the drug supply problem is Hospira, the only pharmaceutical company that produces the anesthetic sodium thiopental.

"We are working to get it back on the market and we anticipate we will by 2011," Hospira spokesman told AFP.

The US Food and Drug Administration does not approve the drug's use in lethal injections and Hospira does not sell it for that purpose, though prison officials make significant use of sodium thiopental in executions.

"This is an anesthetic agent that is used by hospital and it is not indicated for capital punishment," Rosenberg added. "We do not make it for that, we don't support its use in that procedure."

He noted that Hospira does not disclose sales of the drug because it is not a big seller for the company.

Death row inmates are injected intravenously with three drugs once strapped in the death chamber: first they are put to sleep with sodium thiopental, pancuronium bromide then paralyzes their muscles and stops their breathing, and finally, potassium chloride stops their heart.

Two states -- Ohio in the Midwest and Washington in the Northwest -- have opted to carry out executions by injecting only sodium thiopental, but at very high and deadly doses.

The supply dry-up nationwide has prompted Kentucky Governor Steve Beshear to announce he would only sign one of the three execution orders pending on his desk.

"The Kentucky Department of Corrections has a sufficient amount of sodium thiopental for one execution and that amount expires on October 1, 2010," he added in a statement.

Gregory Wilson, who has been on death row for 22 years, will thus be executed on September 16 with the state's last dose of the drug.

But his fellow inmates Ralph Baze and Robert Foley, who like Wilson have also exhausted all their appeals, will be granted an additional, if somewhat accidental, reprieve.

In Oklahoma, authorities only have enough sodium thiopental for one execution although two are scheduled -- for October 14 and 15.

A federal judge stayed the execution of Jeffrey Matthews in mid-August on the day he was due to be put to death because the state planned to use a different anesthetic in what his lawyers labeled "nothing more than experimental."

"The Oklahoma attorney general's office has asked the court to lift the stay on that case because we weren't able to obtain the drug on time to carry out the execution on the previous protocol," spokesman Jerry Massie said.

"So we'll waiting for a hearing" to determine whether to postpone one of the executions, he added.

Rosenberg said Hospira does not know which states have used up their supplies of sodium thiopental because a lot of the firm's products are sold through distributors.

A dozen US states regularly perform the death penalty. Texas and Ohio are the most active, with 16 and six executions respectively this year.

In Texas, officials say the lethal injections will go forward.

"We have two executions currently scheduled and we do have a sufficient amount of supply for those executions," said Michelle Lyons, a spokeswoman for the Texas Department of Criminal Justice.

Lyons said she could not confirm whether Texas had enough of the drugs to perform any future executions this year.

Ohio also made similar claims, though it is said to be running short on its supply of sodium thiopental, which it uses more than any other state.

"We are declining to provide specific information on this issue in the interest of security," said Ohio Department of Rehabilitation and Correction spokeswoman Julie Walburn.