A gauge of U.S. corporate credit risk rose for a third day,reaching the highest in six months, as concern mounts that theFederal Reserve will start scaling back record bond-buying that hasbolstered debt markets.

The Markit CDX North American Investment Grade Index, acredit-default swaps benchmark that investors use to hedge againstlosses or to speculate on creditworthiness, increased 1.8 basispoints to a mid-price of 94.9 basis points at 12:34 p.m. in NewYork, according to prices compiled by Bloomberg. The gauge, tradingat the highest level since December, has surged 10.8 basis pointssince June 14, heading for its biggest weekly increase since May2012, excluding rolls into new series.

Investors' confidence in corporate debt has plunged since FedChairman Ben S. Bernanke said June 19 that the central bank maypare $85 billion of monthly bond purchases this year and end it inmid-2014 if the economy achieves the Fed's objectives. The Fed'sstimulus measures, known as quantitative easing, have suppressedinterest rates, pushing investors into riskier assets such ascorporate bonds in search of higher yields.