The PSNI Chief Constable has decided to retain on duty the remaining 225 members of the Full Time Reserve until the end of March next year, subject to funding being secured from the Northern Executive.
A statement said Matt Baggott had taken the decision as part of the overall policing strategy to release officers back onto the front line.
The PSNI said the move would also provide additional support to the increased operational work to disrupt the activities of what they called criminal terrorists.
It is estimated the decision will cost £6 million pounds.
Last month the Police Federation urged the Chief Constable to retain the reserve because of the increasing threat from dissident republicans.
The disbandment of the Reserve by March 2011 is required under the terms of peace process policing reforms that saw the PSNI replace the RUC under the Patten reforms 10 years ago.
The changes have been the source of intense political argument.
Unionists view the Reserve with deep admiration, crediting its officers for holding the line in the dark days of the Troubles.
However, nationalists and republicans have a very different view, holding some reservists responsible for abuses against their communities during the conflict.