* Deal to extend OPEC-led production cut failed to impress market
* U.S. adds rigs for record 19th straight week
* Oil inventories have dipped, but remain near records (Adds comment, bullet points, updates prices)
By Henning Gloystein
SINGAPORE, May 29 (Reuters) - Oil prices fell on Monday as a relentless rise in U.S. drilling undermined an OPEC-led push to tighten supply.
Trading activity will be subdued on Monday due to public holidays in China, the United States and Britain.
Brent crude futures LCOc1 were trading down 15 cents, or 0.3 percent, at $52.00 per barrel at 0253 GMT.
U.S. West Texas Intermediate (WTI) crude futures CLc1 were down 17 cents, or 0.3 percent, at $49.63 per barrel.
The Organization of the Petroleum Exporting Countries and some non-OPEC producers agreed last week to extend a pledge to cut production by around 1.8 million barrels per day (bpd) until the end of the first quarter of 2018. But the decision did not go as far as many investors had hoped and led to a heavy sell-off. initial agreement, in place since January, would have expired in June this year. immediate market reaction to the May 25 OPEC decision is indicative of the weaker-than-expected impact production cuts had on bloated global crude stocks over H1 2017," BMI Research said in a note.
Despite the ongoing cuts, oil prices have not risen much beyond $50 per barrel.
Much of OPEC's success will depend on output in the United States C-OUT-T-EIA , which is not participating in the cuts and where production has soared 10 percent since mid-2016 to over 9.3 million bpd, close to top producer levels Russia and Saudi Arabia.
U.S. drillers have now added rigs for 19 straight weeks, to 722, the highest amount since April 2015 and the longest run of additions on record, according to energy services firm Baker Hughes Inc BHI.N . all of the recent U.S. output increases have been onshore, from so-called shale oil fields.
Even if the rig count did not rise further, Goldman Sachs (NYSE:GS) said it estimates that U.S. oil production "would increase by 785,000 bpd between 4Q16 and 4Q17 across the Permian, Eagle Ford, Bakken and Niobrara shale plays."
Analysts say that reducing bloated global fuel inventories will be key to reining in ongoing oversupply.
"It's going to be all about inventories and whether they fall as much as OPEC thinks," said Greg McKenna, chief market strategist at futures brokerage AxiTrader.
While it is hard to come by reliable global oil inventory data, regional stock levels for the United States, Europe and parts of Asia suggest that inventories have dipped in recent weeks, albeit from record levels.
<^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Oversold: Oil traders punish OPEC for promising too much
ANALYSIS-OPEC ponders how to co-exist with U.S. shale oil
OPEC oil cut extension renews Asia's crude supply worries