Oil

Crude oil futures clung to gains in volatile trading as the U.S. front-month August contract headed to expiration on Tuesday, with the weaker dollar providing support.

Oil prices rose about 1 percent on Tuesday, reversing early losses, after it became apparent that a nuclear deal between Tehran and six global powers will not immediately remove sanctions placed on Iranian crude exports.

Oil prices came off their lows on Monday after a Tehran official indicated the Islamic Republic might miss another deadline in securing a nuclear deal integral to lifting Western sanctions on its crude exports.

The global oil market should be more balanced next year as China and the developing world increase oil consumption while supply of shale oil from North America and other regions grows more slowly, OPEC said on Monday.

U.S. crude futures fell almost 2 percent on Wednesday as a surprise build in stockpiles pushed the market back down toward the three-month low it touched the previous session.

U.S. crude sank for a second straight day on Tuesday as a near-bankrupt Greece and China's stock market losses sparked an investor flight to safe havens, with technical selling threatening to push oil further into a bear market.

Oil prices rose about 1 percent on Thursday after tame U.S. jobs and economic data signaled the Federal Reserve would be less hasty to raise interest rates while a surge in gasoline futures drove expectations for more crude demand.

Oil prices slumped on Wednesday, with U.S. crude headed for its sharpest daily loss since early April.

Oil prices bounced from three-week lows on Tuesday, with U.S. refined fuels markets leading the rally on bets for strong summer demand, even as Greece's move toward a debt default threatened to jolt global markets.

Crude futures hit 3-week lows on Monday as Greece shut its banks and imposed capital controls, causing widespread risk aversion, while Iran looked likely to extend nuclear negotiations with the West to export more of its oil into an oversupplied market.

Oil prices rose modestly on Wednesday but were under pressure ahead of key U.S. supply data as investors remain wary of the continuing Greek debt negotiations.