Argentina is struggling to win over U.S.-based investors on a bond exchange designed to lower refinancing risks and possibly give it more leverage in negotiations with holdout creditors, Reuters reported yesterday. The sovereign, which launched a tender and exchange offer on local law bonds yesterday, may find a healthy local bid from the state-owned pension system. Yet several U.S.-based holders of Argentine debt said that they had refused to take part in the deal, citing its poor economics and possible legal risks.