Oil prices edged down on Tuesday, weighed by expectations of an OPEC+ output hike in August and concerns of economic slowdown driven by prospects of higher US tariffs. Brent crude futures for September delivery fell 16 cents, or 0.24%, to $66.58 a barrel by 00:00 GMT US. West Texas Intermediate crude declined 20 cents, or 0.31%, to $64.91 a barrel.