Investing.com - Oil turned lower Tuesday after modest gains earlier on in the session as OPEC reported an increase in output in May.
U.S. crude was off 13 cents, or 0.28%, at $45.95 at 8:00 ET. Brent shed 8 cents, or 0.17%, to $48.21.
In its monthly report, OPEC cited secondary sources as saying the output of the cartel rose by 336,000 barrels a day to 32.14 million due to higher output by Libya, Nigeria and Iraq.
Libya and Nigeria were exempt from an accord by OPEC and non-OPEC producers to curb output by 1.8 million barrels a day.
The accord was extended in May by another nine months to March of next year.
Iraqi output last month unexpectedly rose by 44,000 barrels a day to 4.424 million barrels.
U.S. American Petroleum Institute stockpile data are due for release later in the session.
These will be followed Wednesday by the official Energy Information Administration weekly inventories report.
The EIA is forecast to report a fall in U.S. crude stocks of 2.955 million barrels in the latest week.
Higher U.S. output has reduced the impact of the output cut accord.
The number of rigs operating in the U.S. has risen for 21 weeks in a row.