Oil slipped further below $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.
Oil rose on Tuesday, supported by an Opec-led effort to cut output while rising production elsewhere kept prices within the narrow ranges that have contained them so far this year. Brent crude was 80 cents higher at $56.39 a barrel by 1425 GMT. US light crude was up 70 cents at $53.63.
Oil prices edged higher on Friday in response to the possibility of new sanctions on Iran after US President Donald Trump said "nothing is off the table" in response to its test launch of a missile.
Oil prices fell on Monday as increased exports from Iran undermined efforts by other oil producers to curb a global fuel supply overhang and as US drillers increased activity for a 10th straight week.
Oil prices are on track for their biggest annual percentage gain since 2009 on the back of an agreement struck between Opec and non-Opec countries to cut crude production output.
Oil fell more than 2 percent to its lowest in three months on Monday, as the prospect of another year of oversupply and weak prices overshadowed chances OPEC will reach a deal to cut output.
Oil prices reversed early losses to push higher on Thursday as markets recovered from their initial shock at US President-elect Donald Trump's surprise victory, although traders said that crude fundamentals remained weak.
Oil edged above $50 a barrel on Thursday as a further drop in US crude inventories countered investor doubts that OPEC will be able to implement a production cut.
Oil prices edged up on Wednesday, supported by record Indian crude imports and upcoming talks between OPEC producers and other oil exporters on curbing output to end a glut in the global market.