Oil rose to a 2015 high of $67 a barrel on Monday supported by expectations the crude supply glut will ease and after weak Chinese factory activity reinforced views stimulus measures would be rolled out.
The collapse of oil prices in 2014 has prompted expectations that supply growth in higher-cost crude producers such as the United States will slow. On Friday, oil services firm Baker Hughes Inc. said the number of U.S. active rigs had fallen for a record 21 weeks in a row.
Brent crude was up 56 cents at $67.02 a barrel by 1245 GMT (8.45 a.m. EDT), after hitting a 2015 peak of $67.10. U.S. crude gained 22 cents to $59.37. The U.S. benchmark hit its highest this year at $59.90 on May 1.
"The market is expecting the tightening in the second half of the year," said Eugen Weinberg, analyst at Commerzbank.
"We argue this dynamic is hardly fundamentally sound," he said of the market's rally. "There has yet to be any noticeable drop in U.S. oil production."
A public holiday in Britain on Monday is likely to limit trading volume.
Brent has rallied more than 40 percent from a near six-year low of $45.19 in January, supported by expectations of tighter future supply and demand balance, as well as a weaker dollar and Middle East tension.