NEW YORK, Jan. 16 (Xinhua) -- Oil prices retreated on Tuesday as investors were looking for excuses to lock in gains after recent solid gains.

Traders became cautious after recent rally, but analysts said firm demand underpinned prices near a high level.

On the economic front, the number of rigs operating in U.S. oil fields rose by 10 to 752 last week, the biggest increase since June, according to oilfield service firm Baker Hughes' weekly report released last Friday.

The West Texas Intermediate for January delivery decreased 0.57 U.S. dollar to settle at 63.73 dollars a barrel on the New York Mercantile Exchange, while Brent crude for March delivery shed 1.11 dollars to close at 69.15 dollars a barrel on the London ICE Futures Exchange.