Sept. 10 (Bloomberg) — U.S. government debt fell for a fifth day, the longest skid in three months, amid concern investors are underestimating when the Federal Reserve will raise borrowing costs next year.

Yields on benchmark 10-year notes rose alongside those of European bonds, reaching the highest in a month, before the U.S. auctions $21 billion of the securities. Treasuries are the world's worst-performing bonds this quarter as the Fed prepares to end its bond buying while the European Central Bank introduced additional stimulus. Analysts said data this week will show jobless claims fell and retail sales increased, adding to the case for the Fed to raise rates.

"There's some nervousness over Fed policy," said Thomas di Galoma, head of fixed-income rates at ED&F Man Capital Markets in New York. "As we get closer to ending quantitative easing, there's always a risk the Fed comes out and says something a little bit more hawkish. We're starting to see a bottom in global rates in general."