NEW YORK--U.S. oil futures slid for a seventh-straight session Monday on strengthened expectations that halted Libyan exports would return to the global market.

Light, sweet crude for August delivery settled down 53 cents, or 0.5%, at $103.53 a barrel on the New York Mercantile Exchange. Futures posted their longest losing streak since December 2009.

Brent crude on the ICE futures exchange fell 40 cents, or 0.4%, to $110.24 a barrel. Futures have fallen for six-straight sessions, the longest losing streak since April 2013.

Prices spiked to nine-month highs in mid-June on concerns that an insurgency in Iraq would cut off production there, but futures have slumped in recent weeks as Iraqi exports remained uninterrupted and Libyan output looked likely to increase.

The Libyan government has lifted a ban on loadings from two oil ports, Es Sider and Ras Lanuf, said Mohammad el-Harari, a spokesman for the state-owned National Oil Co.

The ports have been occupied by rebels since late July 2013.

Es Sider and Ras Lanuf normally ship 560,000 barrels a day together, nearly half of the country's daily export capacity of 1.3 million barrels.

Though past agreements to increase Libya's oil output have been unsuccessful, "we believe the scope for a return of production is greater this time," BNP Paribas analysts said in a note Monday.

The Libyan ports have "been offline a long time," said John Kilduff, founding partner at Again Capital in New York. "There's a big incentive there to get the money flowing."

Brent, the global oil benchmark, has pared nearly all the gains made last month after insurgents seized several cities in Iraq.

Though the political situation in Iraq remains unstable, oil traders had taken on so many bets on higher prices that the market was vulnerable to a pullback, said Tim Evans, analyst at Citi Futures Perspective.

Money managers, including hedge funds and pension funds, reduced their total bet on rising Nymex oil prices by 4.4% in the week ended Tuesday, according to data released Monday by the U.S. Commodity Futures Trading Commission.

"Money managers look to be more inclined to pare back on their exposures rather than to just keep buying," Mr. Evans said.

Front-month August reformulated gasoline blendstock, or RBOB, settled down 3.08 cents, or 1%, to $2.9890 a gallon. Demand for gasoline typically falls after the Independence Day holiday weekend, Mr. Kilduff said.

August diesel settled down 1.39 cents, or 0.5%, to $2.9145 a gallon.

(Benoît Faucon contributed to this article.)