Oil prices cut early losses after Iraq said it was willing to "shoulder responsibility" for some of OPEC's planned production cuts and as U.S. government data showed crude inventories fell last week.
But gains were capped by investor doubts that OPEC will agree to a production cut large enough to make a significant dent in the global glut of crude.
OPEC's deal faced potential setbacks from Iraq's call for it to be exempt. Baghdad had said it needs oil revenues to fight Islamic State militants and questioned whether it should cut from the levels of OPEC's estimates or its own, higher, production figures.
But Prime Minister Haider al-Abadi told reporters on Wednesday in Baghdad that Iraq is willing to cut its crude oil output as part of OPEC's plan to reduce global supply and boost crude prices.
Abadi's comments are the clearest indication so far that Baghdad will support an OPEC plan to cut production by 4 percent to 4.5 percent when it meets on Nov. 30 in Vienna.