NASHVILLE, Tenn. (AP) — Tennessee's attorney general on Thursday asked the state Supreme Court to set eight execution dates before June 1, saying officials are uncertain they get lethal injection chemicals after that.

Juries delivered death sentences for the eight men decades ago, and each has exhausted his three-tier appeals process in state courts and the U.S. Supreme Court, Attorney General Herbert Slatery wrote in a court filing.

The request could bring a wave of executions to a state that hasn't put anyone to death since 2009. One other man who used his three-tier appeals options is already scheduled for execution in August.

Tennessee uses a three-drug combination because death-penalty opponents worked with pharmaceutical companies to prevent the state from obtaining the single drug it used, pentobarbital, during an unsuccessful lawsuit over its use, the attorney general's filing states.

The Department of Correction is still trying to find a source of pentobarbital, but it hasn't succeeded and currently has none on hand, the filing states. "As a result, the Department deemed it necessary to provide an alternative drug combination to ensure it could comply with its statutory obligation to carry out death sentences by lethal injection when ordered to do so."

The attorney general cited "ongoing difficulty" getting necessary lethal injection drugs.

The filing also says the defendants now want to delay execution to challenge the three-drug mix, which includes the sedative midazolam, the muscle-relaxer vecuronium bromide and potassium chloride to stop the heart. The U.S. Supreme Court and other federal appeals courts have rejected constitutional challenges to using midazolam as the first drug in a three-drug combination, the filing states.

The attorney general wants execution dates for eight men convicted of first-degree murder: Donnie Johnson, Stephen Michael West, Edmund Zagorski, Leroy Hall, Abu-Ali Abdur'Rahman, Charles Walton Wright, Nicholas Todd Sutton and David Earl Miller.

Three other men are scheduled for 2018 executions. One of them, Billy Ray Irick, has exhausted his appeals. The 59-year-old convicted of raping and killing a 7-year-old Knoxville girl in 1985 is scheduled to die Aug. 9.

In Tennessee, executions are carried out through lethal injection unless the drugs are unavailable, in which case, the electric chair will be used.

Additionally, death row inmates whose offenses came before January 1999 can choose the electric chair or lethal injection. The last time Tennessee put someone to death by electric chair was 2007.

There are currently 59 men and one woman on death row in Tennessee.