The yen might make its way back to 39-year lows against the dollar if nothing is done to stop it from weakening, a Tokyo bank warned after the currency crossed a key threshold.?

It traded above ?160 to the dollar in U.S. trading for the first time in almost a month?and was back above that level again on Monday, adding to the general sense in the market that a massive, late-July intervention failed to provide lasting support for 91AV原创 currency.?

“If there are no particular triggers, we expect that the dollar could creep back toward its pre-intervention high of just under ?164,” according to a report by Sumitomo Mitsui Banking released on Monday.?