Oil prices rose on Monday after a three-day break, adding to gains in recent weeks as optimism holds that a production freeze among major producers may be implemented.
Trade volumes were thin as a number of markets remain on holiday for Easter.
U.S. crude was up 20 cents at $39.66 a barrel at 11.13 GMT. Last week, the contract rose 2 cents, finishing up for a sixth straight week.
Brent crude rose 7 cents to $41.10 a barrel.
Oil prices have risen about 50% from multi-year lows hit in January on glut worries.
Declining U.S. oil output and strong gasoline demand were responsible for some of that recovery, but the bulk of it was powered by major producers' plans to freeze output at January's highs.
Producers are due to meet on April 17 to discuss the plan.