Investing.com - Oil edged lower Monday with the focus on compliance with agreed output cuts.
Brent crude shed 6 cents, or 0.11%, to $55.39 at 08:00 ET. U.S. crude lost 10 cents, or 0.19%, to $52.27.
Trading was thin, with the U.S. markets closed for a public holiday.
OPEC and non-OPEC producers have agreed to cut output by some 1.8 million barrels a day in the first six months of this year.
Saudi Arabia and Kuwait have already moved to decrease production but doubts remain about other producers.
Baker Hughes data Friday showed the number of rigs operating in the U.S. falling for the first time in 10 weeks.
Increased activity by North American shale producers could undermine efforts to address a global supply glut.