0058 GMT - Most Asian currencies strengthen slightly against the dollar on skepticism over the U.S. Treasury Department's bond buyback plan. The plan "failed to anchor long-term [U.S.] yields for now, raising doubts whether Treasury buybacks can sustainably lower borrowing costs against persistent fiscal and structural pressures," strategists at OCBC Group Research say in a report. "So far, the surprise buyback programme has coincided with a weaker USD, higher gold prices and rising breakeven inflation rates," the strategists add. The U.S. dollar falls 0.5% to 1,387.30 won and edges 0.1% lower to 1.2712 Singapore dollars, LSEG data show.