By Mark Felsenthal

WASHINGTON, June 5 (Reuters) - A senior U.S. Federal Reserve official said on Friday that a recent surge in long-term interest rates would be worrisome if fueled by anxiety about inflation but that does not seem to be the case.

Last week, the spread between U.S. 2-year and 10-year Treasury notes US10YT=RR hit a record 2.75 percentage points and 10-year yields are currently above 3.8 percent, up from 3.16 percent a month ago.

The jump in yields and a related rise in U.S. mortgage rates threatens to undermine the hoped-for U.S. economic recovery before it even gets started.

Speaking at a conference sponsored by the Fed and the Journal of Money, Credit and Banking, San Francisco Federal Reserve Bank President Janet Yellen did not close the door on the possibility inflation concerns were driving up yields, but made clear she was doubtful.

"While I have not found these arguments convincing so far, the recent rise in Treasury rates, if it is reflective of such concerns, is disconcerting," she said, expressing confidence the central bank would be able to keep price rises in check.

The Fed in March launched a program to buy longer-term U.S. Treasury bonds as part of its aggressive efforts to revive credit markets and pull the economy out of the deepest recession in decades.

But the rise in yields raises the specter that markets fear massive U.S. monetary and fiscal stimulus will undermine price stability when the recovery takes hold.

Officials have committed to hold overnight interest rates near zero for an extended period to ensure a recovery, and have discussed expanding U.S. Treasury purchases to accelerate the economy's return to health.