Oil prices fell on Tuesday on anticipation of another weekly build in U.S. crude stockpiles.
Position squaring ahead of the expiry of the front-month contract in U.S. crude also accounted for a large part of activity, traders and analysts said.
"The bears seem to be having an edge this week after the strong gains of the past week," said Gene McGillian, analyst at Tradition Energy in Stamford, Connecticut.
U.S. crude's front-month, which expires at the close of Tuesday's session, was down 43 cents, or almost 1 percent, at $55.95 a barrel by 1:23 p.m. EDT (1723 GMT).
A preliminary Reuters survey on Monday showed that U.S. crude inventories likely rose by 2.4 million barrels last week, for a 15th straight week of builds.
The American Petroleum Institute, an industry group, will issue its own reading on the inventory situation at 4:30 p.m. EDT, before official stockpile data due from the government on Wednesday.
U.K. North Sea Brent crude, the more widely used benchmark for oil, slipped $1, or 1.5 percent, to $62.45 a barrel.
Traders said Brent was pressured by the global oversupply in oil, including U.S. crude, even as worries about a civil war in Yemen provided some support.
Despite Tuesday's declines, both Brent and U.S. crude remained up more than 15 percent for April after gains over the past two weeks on speculation that the selloff in oil that began last summer is losing steam.
Some analysts disagree that the market is on the cusp of a longer-term recovery.
Commerzbank's Carsten Fritsch sees Brent heading down to the low $50s a barrel last seen in March.
The head of the world's largest oil trading company, Vitol, said oil prices were likely to slip as refineries undergo maintenance work in the second quarter.
"We will probably see another dip in oil prices in Q2", but not below January lows, Ian Taylor told Reuters on the sidelines of an industry conference in Lausanne, Switzerland.
(Reporting by Christopher Johnson and Jacob Gronholt-Pedersen; Editing by Alison Williams and Meredith Mazzilli)