* U.S. crude production has reached pre-Harvey storm levels
* OPEC to discuss potential extension of production cut on Friday
* Brent curve has moved into backwardation since July (Updates prices)
SINGAPORE, Sept 21 (Reuters) - Oil markets dipped on Thursday, weighed down by rising crude inventories and production in the United States as well as a stronger dollar, which potentially hampers fuel consumption in countries that use other currencies at home.
Brent crude futures, the international benchmark for oil prices, were at $56.12 a barrel, as of 0656 GMT, down 17 cents, or 0.3 percent, from their last close.
U.S. West Texas Intermediate (WTI) crude futures were at $50.58 per barrel, down 11 cents or 0.2 percent.
Traders said a strengthening dollar weighed on Brent, while rising crude stocks and production in the United States pulled down WTI.
U.S. commercial crude oil inventories <C-STK-T-EIA> rose for a third straight week, building by 4.6 million barrels in the week ending Sept. 15 to 472.83 million barrels.
Meanwhile, U.S. oil production has largely recovered from the shutdowns following Hurricane Harvey, currently standing at 9.51 million barrels per day (bpd), up from 8.78 million bpd directly after the storm hit the U.S. Gulf Coast. <C-OUT-T-EIA>
However, WTI did receive some support from a strong draw in gasoline stocks by 2.1 million barrels to 216.19 million barrels, traders said.
Markets could tighten should the Organization of the Petroleum Exporting Countries (OPEC) extend a production cut aimed at tightening supplies and propping up prices.
OPEC will meet in Vienna on Friday and discuss extending its deal to cut production with some non-OPEC producers that has been in place since January. The current deal will expire at the end of March 2018.
Under the deal, OPEC members and some non-OPEC countries pledged to cut production by 1.8 million bpd to tighten the market and prop up prices.
But, because OPEC members Libya and Nigeria were exempted from cutting and non-compliance by others, markets remain amply supplied, triggering calls for more action.
"Exempt members Libya and Nigeria may be bought into the fold... There also remains the possibility that an extension of the agreement or an increase in the cuts may be announced," said Jeffrey Halley, of futures brokerage OANDA.
There are indicators that the supply cuts are having the desired effect.
Front-month Brent futures prices have risen by more than a quarter since June. Also, over the past two months the structure of the Brent forward curve has moved into backwardation, when prices for immediate delivery are higher than prices for later delivery, from contango.
The shift is seen as an indicator of a tightening market as it incentivises the immediate sale of oil rather than holding it in storage.
(Reporting by Henning Gloystein; Editing by Christian Schmollinger and Sherry Jacob-Phillips)