TOKYO, June 17 (Reuters) - The Bank of Japan may start debating ways to phase out its extraordinary stimulus programme, such as by ditching negative interest rates, around the time Governor Haruhiko Kuroda"s term ends in 2023, said former central bank executive Eiji Maeda. Even if the BOJ were to raise its short-term rate target from the current -0.1%, it will likely maintain a 0% cap on long-term rates due to the need to help keep borrowing costs low for the government"s fiscal spending, he said. In an interview with Reuters conducted on Wednesday, Maeda also said the BOJ could consider buying green bonds in the future though any such step would be "some time away." Reporting by Leika Kihara; Additional reporting by Takahiko Wadao Editing by Chang-Ran Kim Our Standards: The Thomson Reuters Trust Principles.