Japan may conduct joint yen intervention "at any time" and signal the chance of faster-than-expected interest rate hikes to stem the currency's falls, said Tokyo's former top currency diplomat Mitsuhiro Furusawa. The yen is "clearly too weak" at current levels and hurting the economy by boosting import costs, Furusawa said, adding that Tokyo and Washington could step in again if the yen returns to levels hit before their joint intervention last month.