LINCOLN, Neb. (Reuters) - The state of Nebraska said on Thursday it has purchased a new supply of lethal injection drugs and will move to execute one of the men convicted in one of the deadliest bank robberies in U.S. history.

Attorney General Doug Peterson said in a statement that his office would move to have an execution date set for Jose Sandoval, 38, within 60 days.

Twenty-three people have been executed in the United States so far this year, compared with 20 in 2016 and 28 in 2015, according to the Death Penalty Information Center.

Nebraska’s most recent execution occurred in 1997.

The state had been without a method to execute people for several years due to a shortage of the lethal drugs required. Nebraska’s supply of sodium thiopental, used to knock out the inmate before two other drugs were administered, expired in December 2013 and the state was unable to buy more due to difficulties in procuring it.

The Nebraska Legislature in 2015 repealed the state’s death penalty and then overrode Republican Governor Pete Ricketts’ veto of the measure. However, death penalty proponents then succeeded in placing the issue on the ballot and voters rescinded the repeal in 2016.

Sandoval and three other men were convicted of killing five people during the robbery of a U.S. Bank branch in Norfolk, Nebraska, in September 2002.

The state previously had a three-drug, lethal injection protocol calling for a dose of sodium thiopental, followed by pancuronium bromide to cause paralysis and a dose of potassium chloride to stop the heart.

But sodium thiopental is now extremely difficult to purchase. Nebraska and several other states that used it in their executions were forced to buy the drug overseas when the last U.S. manufacturer quit making it in 2010 because of death penalty opposition from customers.

Sodium thiopental was then banned for export by the European Union. It is still made in India and China, but defense lawyers have questioned its quality.

Nebraska officials said the state now plans to use diazepam, fentanyl citrate, cisatracuriam besylate and potassium chloride.

State corrections spokeswoman Dawn Renee Smith said the drugs were purchased in the United States. She declined to name the supplier.

(This story corrects spelling of Jose Sandoval’s name in second paragraph.)