The yen rose for a third straight session on Monday, keeping traders on alert for further intervention after Tokyo and Washington stepped into the foreign exchange market last week to support Japan's currency. Japan's finance ministry confirmed it had engaged in joint yen-buying intervention with the U.S. on Friday, while Bank of Japan data showed Tokyo may have bought as much as $58.97 billion worth of yen on Thursday. The Japanese currency rose 1% in the Asian morning to a high of 155.20 per dollar, its strongest level in about three months, before paring some gains to last trade up 0.45% at 156.65. Oil prices sank more than $4 a barrel after U.S. President Donald Trump held back from a fresh attack on Iran, undermining support for the safe-haven greenback. The dollar index was little changed at 99.79, while the euro was up 0.03% at $1.1525 after hitting a fresh one-and-a-half-month high at $1.1559 in Asian trade.