Currency markets drifted on Thursday, with the Japanese yen softening to 157.85 per dollar after giving back some of the gains from a historic U.S.-Japan joint intervention that had pushed it to 155.20 earlier in the week. The dollar index rose 0.1% to 99.77, edging away from a six-week low, as investors remained cautious amid ongoing tensions in the Gulf. A proposed deal between Iran and Oman could give Tehran control over inbound traffic through the Strait of Hormuz, though the U.S. has not commented on the proposal and has previously insisted it would never agree to such terms.