This action is the conditional approval of the Ohio oxides of nitrogen (NO<INF>X</INF>) State Implementation Plan (SIP). This document also contains USEPA's response to the adverse comment from American Electric Power Services Corporation (AEP) sent to USEPA following publication of the original direct final approval of the Ohio NO<INF>X</INF> plan on January 16, 2003, which was subsequently withdrawn because of receipt of an adverse comment. USEPA is conditionally approving the Ohio NO<INF>X</INF> plan following the receipt of a commitment from the Director of Ohio EPA to change the flow control date in the State plan from 2006 to 2005. On June 25, 2003, Ohio sent a letter to USEPA containing a commitment to take specific enforceable measures by which the flow control date will be changed. These enforceable measures include: timing by which Ohio will begin the public process; timing when the amended rule will be filed with the Joint Committee on Administrative Rule Review; timing of the public hearing; and time span when the amended rule process will be complete. Ohio EPA expects the flow control date in the rule to be changed approximately six months from the date of the commitment letter. USEPA found that the commitment is acceptable and, therefore, USEPA is taking action to conditionally approve the Ohio plan based on the commitment from Ohio to submit the revised rule by December 26, 2003. We will populate the compliance accounts of units listed in the State's rule after September 4, 2003, so that respective Ohio sources can participate in the NO<INF>X</INF> trading program.