US Treasury yields rose to their highest level in six months and stocks fell on Wednesday, fuelling concern that rising mortgage rates could damp a nascent US economic recovery. The yield on the benchmark 10-year Treasury note rose 24bp to 3.74%, a level last seen in mid-November. The 10-year note has climbed from lows of 2.1% in December. While short-term yields remain stable, longer-term yields have been volatile for several days, raising questions about whether the Fed will have to increase its planned purchases of Treasuries.