STOCKHOLM (Reuters) - The Nordic region's defence capabilities would be strengthened if Sweden and Finland joined NATO, allowing joint defence planning within the framework of the alliance, Sweden's defence minister told Swedish radio on Tuesday.

       "(If Sweden and Finland join NATO) there will be the effect that we use each others' strengths and advantages and fully complement each other and also carry out operational planning," Defence Minister Peter Hultqvist of the ruling Social Democrats said.

       "If so, the effect will be that we become stronger together. This is something that can happen if we choose to join NATO," he told the public broadcaster.

       Sweden already has defence agreements with its Nordic neighbours.

       The Social Democrats will decide on May 15 whether to drop decades of opposition by the party to NATO membership, a move that would almost certainly lead to Sweden asking to join the 30-nation alliance.

       Russia's invasion of Ukraine has sparked a rethink of security policy in Sweden and Finland. The Finnish president, Sauli Niinisto, is this week expected to announce his support for an application.

       Hultqvist, a long-time sceptic towards Swedish NATO membership, declined to say in the interview what his current stance was.

       Denmark, Norway and Iceland are already members of NATO.

       (Reporting by Anna Ringstrom; Editing by Simon Johnson)