(Reuters) - The state of Ohio plans to resume the execution of condemned inmates in January, ending a three-year pause in carrying out death sentences, under a new lethal-injection protocol designed to meet U.S. Supreme Court approval, prison officials said on Monday.

The Ohio Department of Rehabilitation and Correction (DRC) said it would proceed in January with the scheduled execution of Ronald Phillips, convicted and sentenced to death for the 1993 rape and murder of a 3-year-old girl.

Phillips, 42, would be the first Ohio inmate put to death since January 2014. Ohio, one of 31 U.S. states with capital punishment, instituted a death penalty moratorium in 2015 due to difficulty in obtaining the drugs needed to perform lethal injections.

Phillips' attorney did not immediately respond to a request for comment. Phillips is incarcerated at the Chillicothe Correctional Institution in southern Ohio.

Ohio has 26 people on death row, according to the DRC, with executions scheduled until October 2019.

The correction department said it has presented a federal judge with a revised execution protocol that includes a three-drug combination specifically upheld by the U.S. Supreme Court last year as permissible.

The department said a similar drug combination - consisting of midazolam, rocuronium bromide and potassium chloride - was used by Ohio from 1999 to 2009.

In January 2014, Ohio became the first state to use a combination of the sedative midazolam and painkiller hydromorphone when it executed Dennis McGuire for the 1993 rape and murder of a pregnant woman.

McGuire's execution, witnessed by his adult children and reporters, took 25 minutes. Witnesses said he gasped and convulsed for 15 minutes.

Last October, the state delayed all scheduled executions until 2017 as it worked to secure a new supply of drugs.

Kevin Werner, executive director of Ohioans to Stop Executions, an anti-death penalty group, said the decision to resume executions was misguided and the state needed to work to ensure the execution process was "fair and accurate."

"This is yet another experiment with at least one untried drug. Ohio's track record is not one that exudes confidence," Werner said by email.

(Reporting by Timothy Mclaughlin in Chicago; Writing and additional reporting by Steve Gorman in Los Angeles; Editing by Matthew Lewis)