COLUMBUS, Ohio — The sole U.S. manufacturer of a key lethal injection drug said Friday it is ending production because of death-penalty opposition overseas – a move that could delay executions across the United States.

Over the past several months, a growing shortage of the drug, sodium thiopental, has forced some states to put executions on hold. And the problem is likely to get worse with the announcement from Hospira Inc. of Lake Forest, Ill.

Hospira said it decided in recent months to switch manufacturing from its North Carolina plant to a more modern Hospira factory in Liscate, Italy. But Italian authorities demanded a guarantee the drug would not be used to put inmates to death – an assurance the company said it was not willing to give.

“We cannot take the risk that we will be held liable by the Italian authorities if the product is diverted for use in capital punishment,” Hospira spokesman Dan Rosenberg said.

Italian Health Ministry officials were not immediately available for comment.

Of the 35 states that employ lethal injection, all but Oklahoma use sodium thiopental. In nearly every case, they use it as part of a three-drug combination that sedates and paralyzes the inmate and stops the heart.

There are other, similar sedatives on the market, but substituting one drug for another would require new laws or lengthy administrative processes in some states, and could also lead to lawsuits from death row.

Hospira, the only sodium thiopental-maker approved by the Food and Drug Administration, has long deplored the drug’s use in executions but said it regretted having to stop production, because sodium thiopental has legitimate medical purposes as an anesthetic used in hospitals.

Without providing details, Rosenberg said the company’s state-of-the-art Italian factory was the only plant capable of manufacturing sodium thiopental.