NEW YORK (Reuters) - Oil prices fell more than 1 percent on Wednesday on expectations of another surge in U.S. inventories, retreating from multi-week highs hit in the previous session after OPEC signaled optimism over its deal with other producers to curb output.
In post-settlement trade, prices pared losses sharply after data from industry group the American Petroleum Institute (API) showed a surprise drop in U.S. crude stocks last week as imports slumped.
U.S. crude inventories fell 884,000 barrels in the week to Feb. 17, compared with analysts' expectations for an increase of 3.5 million barrels. Before last week, crude stocks have risen for six straight weeks.
Official data from the U.S. Department of Energy's Energy Information Administration (EIA) is scheduled at 11 a.m. EST (1600 GMT) on Thursday, delayed by a holiday on Monday.
Brent crude LCOc1 ended 82 cents, or 1.5 percent, lower at $55.84 a barrel, having touched its highest since Feb. 2 at $57.31 in the previous session.
The U.S. West Texas Intermediate crude April contract CLc1, the new front-month future, settled 74 cents, or 1.4 percent, lower at $53.59.
Both contracts pared losses to trade about 0.8 percent lower in after-hours trade.
Despite the swelling inventories, analysts and traders were largely optimistic about the sustainability of the rally over the last four sessions.
"We've seen a fairly significant increase in crude stocks since the beginning of the year and yet the market has been able to maintain its relative buoyancy," Andrew Lebow, senior partner at Commodity Research Group in Darien, Connecticut, said.
"I think the underlying sentiment is bullish ... what's been key to the market is you've seen the tightening of the spreads, especially in the front."
During a near two-year period of oversupply, the contango or time spread between contracts in the futures markets - when prompt barrels are cheaper than later supplies - deepened.
But the contango has narrowed since the start of the year, when a deal under the Organization of the Petroleum Exporting Countries' umbrella to cut global output took effect, suggesting that the oversupply could be abating.
The discount of the prompt WTI contract to the second month CLc1-CLc2 tightened to as little as 26 cents per barrel on Wednesday, its narrowest since Oct. 20.
Brent crude's spread LCOc1-LCOc2 came within cents of flipping into backwardation - when prompt supplies become most expensive compared with later deliveries - on Tuesday amid optimism over the OPEC deal.
On Tuesday, OPEC Secretary General Mohammad Barkindo said the group and other producers including Russia will boost compliance with agreed output curbs in a bid to boost prices.
Eleven non-OPEC oil producers that joined the OPEC deal have delivered at least 60 percent of promised curbs so far, OPEC sources said on Wednesday, higher than initially estimated.
Goldman Sachs reiterated its outlook for a recovery in prices in the second quarter - WTI to rise to $57.50 and Brent to $59 - before declining respectively to $55 and $57 for the rest of the year.
The investment bank said "while the reduction in oil supplies out of core OPEC in the Gulf and Russia has exceeded our and consensus expectations, the market is starting to doubt that this will be sufficient to translate into large oil inventory draws by the second quarter."
Additional reporting by Sabina Zawadzki in London and Aaron Sheldrick in Tokyo; Editing by Marguerita Choy and Louise Heavens