(REUTERS) - Ohio plans to use a new drug or combination of drugs for executing inmates by lethal injection because its supply of pentobarbital is about to expire, according to a court filing.

Federal Judge Gregory Frost in Columbus, Ohio, disclosed the state's intentions in a court filing on Monday, although the filing was not reported until Thursday. He did not say how the state would execute death row inmates. Judge Frost said lawyers for the state discussed the issue in a conference call last week.

State lawyers said the new execution method would be in place by no later than October 4, in time for the scheduled execution of Ronald Phillips on November 14. It will not be in place in time for the scheduled execution of Harry Mitts, Jr on September 25, the judge's order said.

The Ohio Department of Rehabilitation and Correction did not respond to a Reuters request on Thursday for comment on the filing.

Ohio and other states where capital punishment is legal have reported difficulty finding companies that manufacture pentobarbital. Ohio officials have said the state will run out by the end of September.

Danish pharmaceutical company Lundbeck LLC manufactures the drug and refuses to supply it for executions because the European Union, of which Denmark is a member, forbids the death penalty.

Judge Frost's filing came as part of ongoing legal challenges filed by Ohio death row inmates.