* Consumer sentiment data expected to show more optimism
* Treasuries could stay rangebound in coming sessions
By Luciana Lopez
NEW YORK, May 17 (Reuters) - Prices for U.S. Treasuries drifted lower on Friday after rallying in the previous two sessions as investors weighed whether the Federal Reserve is preparing to taper its asset purchases, even as weak economic data blurred the outlook.
With little data other than consumer sentiment on tap for Friday, Treasuries traded well within Thursday's range. The Thomson Reuters/University of Michigan consumer sentiment data, due to be released at 9:55 a.m. (1355 GMT) is expected to show a brighter outlook in May from April.
Treasuries rallied sharply in the previous two sessions as a spate of disappointing economic data about jobs and inflation underscored potential weakness in the world's largest economy.
The data added to uncertainty about when the Fed might slow or stop its buying of $85 billion per month in Treasuries and mortgage-backed securities, a bid to prop up the U.S. economy and reduce unemployment.
"We still don't know what tapering means, we don't know what it looks like, we don't know the size, we just don't know," said David Ader, senior government bond strategist at CRT Capital Group.
"Today is a day of probably consolidation, price-wise," he said.
Prices for benchmark 10-year Treasuries dipped 3/32 to yield around 1.890 percent from 1.8792 percent late on Thursday.
The 30-year bond traded nearly 10/32 lower to yield 3.112 percent from 3.096 percent late on Thursday.
Thursday's rally saw yields end at a one-week low after having climbed to a two-month high earlier in the week. That rally was potentially overdone, said Jim Vogel, interest rate strategist at FTN Financial in Memphis, Tennessee.
"It's just going to take a little while to even things back out," he added.
Analysts said Treasuries could be rangebound in coming sessions as the uncertainty over the Fed's easing program continues. Vogel said he expects to see a range of 1.85 to 2.015 percent in 10-year yields in coming sessions.