LONDON (Feb 15): Oil slipped further below US$56 a barrel on Wednesday as an industry report showing a large rise in US crude inventories signalled ample supply, even as OPEC achieves record compliance with its supply-cut accord.

US inventories rose by a larger-than-expected 9.9 million barrels last week, the American Petroleum Institute (API) trade group said on Tuesday, ahead of the Energy Information Administration's (EIA) official supply report.

"The inventory trend in the US raises doubts about whether the OPEC production cuts have actually resulted already in a tighter supply situation," said Carsten Fritsch, analyst at Commerzbank.

Brent crude was down 13 US cents at US$55.84 by 1040 GMT, half its level of mid-2014, when a global glut started a collapse in prices. US crude fell 23 US cents to US$52.97.

To support prices, the Organization of the Petroleum Exporting Countries and other producers including Russia are cutting output by almost 1.8 million barrels per day in the first half of 2017.

Although OPEC has made a strong start in complying with the cuts, rising US stocks and a revival of US oil output have limited the price rise.

Analysts expect US crude inventories to have risen by 3.5 million barrels, the sixth straight week of gains, in the EIA report scheduled to be released at 1530 GMT.

"Should this figure be confirmed by the EIA later today, US crude stocks will have risen to a fresh record high," said Stephen Brennock of oil broker PVM, referring to the API's report.

Oil was also pressured by a strong US dollar after Federal Reserve Chair Janet Yellen signalled a faster pace of interest rate rises. Gains in the US dollar make oil more expensive for holders of other currencies.

OPEC in January delivered record compliance of over 90% with its output curbs, according to estimates from the International Energy Agency and figures collected by OPEC's headquarters.

Within OPEC, adherence is mixed. Top exporter Saudi Arabia, keen to make the deal work, said it cut output by more than the amount called for by the agreement.

BMI Research, in a report, said a compliance rate of just 40% by Iraq, OPEC's second-biggest producer, "could prove problematic to group cohesion".

Russia and the other non-OPEC producers have so far delivered smaller cutbacks. The oil minister of Oman, one of the participating non-OPEC countries, said he expected compliance to improve.