Japan could step into currency markets again, potentially in coordination with the United States, if renewed yen weakness deepens, former top currency diplomat Mitsuhiro Furusawa said. He argued the yen is clearly too weak at current levels and is damaging the economy by raising import costs. Furusawa said intervention could come at any time rather than at a fixed exchange-rate threshold, and that a more durable response would require the Bank of Japan to raise interest rates faster and signal that pace more clearly. Tokyo and Washington's joint intervention last month helped lift the yen to around 155.20 per dollar from a 40-year low of 163.99, but the currency has since weakened back to around 159.50. Furusawa said the BOJ should raise rates in September, with follow-up moves likely in December or January and another increase in the next fiscal year beginning in April 2027 if economic momentum holds. He said the central bank likely wants rates around 1.5% to 1.75%, based on its estimate of a neutral rate (a level that neither cools nor overheats growth) of 1.1% to 2.5%. Tokyo Tanshi data showed markets were assigning a 76% chance of a September hike, up from 24% on July 30. Furusawa also said Prime Minister Sanae Takaichi's administration should avoid obstructing BOJ tightening and uphold fiscal sustainability, arguing that a mix of monetary and fiscal policy could help end excessive yen selling and support gradual currency appreciation over time.