TOKYO, Jan 31 (Reuters) - The Bank of Japan should discontinue purchases of risky assets such as exchange-traded funds (ETF) once sustainable achievement of its 2% inflation target comes into sight, one board member was quoted saying at the central bank's January meeting.

Another opinion called for the BOJ to end negative interest rates "at an appropriate timing," as delaying the decision for too long could require subsequent interest rate hikes to be rapid, a summary of the meeting showed on Wednesday.

Under its massive stimulus programme, the BOJ guides short-term interest rates at -0.1% and the 10-year bond yield around 0%. It also buys government bonds and risky assets as part of efforts to reflate growth and achieve its 2% inflation target. (Reporting by Leika Kihara; Editing by Jacqueline Wong)