Oil prices slipped on Tuesday amid rising COVID-19 cases and a possible return of Libyan oil production, which has been down to a trickle since the start of the year.

The more-active September contract for Brent fell 60 cents, or 1.43%, to $41.25 a barrel by 13:49 GMT, paring Monday’s 92 cent gain. The August contract , which expires on Tuesday, fell 69 cents to $41.02.

U.S. crude was down 63 cents, or 1.59%, at $39.07 a barrel.