Oil slipped on Friday, heading for a fourth consecutive weekly settlement within the $75-$80 range, as investors focused on a slowing economy and rising inventories in top consumer the United States.
European stocks traded lower and Asian equities declined ahead of data expected to show U.S. economic growth slowed to 2.5 percent in the second quarter from 2.7 percent in the first quarter.
U.S. September crude shed 64 cents to $77.72 a barrel at 1035 GMT (6:35 a.m. EDT). ICE Brent fell 61 cents to $76.98.
We've got the GDP figures coming out later and maybe people are squaring up a little bit before then just in case it comes in a little bit weak, said Rob Montefusco, a trader at Sucden Financial.
If you go by those horrendous numbers we had on Wednesday, there's plenty of oil stocks around.
A U.S. government report on Wednesday showed crude inventories jumped the most in almost two years last week, by more than 7 million barrels. Industry group the American Petroleum Institute also reported a rise in stockpiles.
The reports showing soaring crude stockpiles in the U.S. had forced prices toward the bottom of the recent price range earlier in the week by signaling weak demand.
The slowdown in the U.S. economic recovery was also flagged by a stream of weak economic data in the past couple of months, and a softer report on Friday could revive fears among investors of a double-dip recession.
Still, U.S. crude on Thursday climbed almost 1.8 percent, the first gain of the week despite falling equities, boosted by a weaker dollar, which makes dollar-denominated commodities cheaper for other currency holders.
The dollar rose against a basket of currencies .DXY on Friday.
Oil has traded in a range between $70 and $80 for almost two months. Prices are unlikely to move above $80 a barrel unless inventories fall, said Mark Pervan, a senior commodities analyst at ANZ in Melbourne.
Industrial output in Japan, the world's third-largest oil user, unexpectedly fell in June and manufacturers expect further declines in coming months, boding ill for the fragile economic recovery.
Members of the Organization of the Petroleum Exporting Countries have said they prefer oil to remain around $70 to $80 a barrel, a level they say encourages investment to sustain and increase production capacity and does not put the global economic recovery at risk.
With prices staying within that range, OPEC production has been climbing steadily and has risen further in July, a Reuters survey showed on Thursday.
(Additional reporting by Alejandro Barbajosa; editing by James Jukwey)