Oil prices slipped on Monday as further increases in U.S. drilling activity undercut an OPEC-led push to tighten supply. [...]

OPEC's success in drawing down inventories may hinge on output in the United States, which is not participating in the cuts. U.S. production has soared 10 percent since mid-2016 to more than 9.3 million bpd, close to top producer levels Russia and Saudi Arabia.