U.K. Business Secretary Vince Cable said the export ban for pentobarbital, pancuronium bromide and potassium chloride would be formalized in a few days, The Guardian reported Friday.
"We oppose the death penalty in all circumstances and are clear that British drugs should not be used to carry out lethal injections," Cable said. "Because of the importance and urgency of the situation this is an issue on which we felt we had to take the lead."
Pentobarbital is a sedative with a range of medical uses, including the treatment of epileptic seizures, and is also used to euthanize animals.
Since late last year, it has been used in the United States for lethal injections because supplies of another drug, sodium thiopental, became scarce.
Britain imposed export controls on sodium thiopental in November after it was discovered a small-scale wholesaler in west London had sold the drug to corrections departments in Georgia and Arizona.