Oil prices slipped on Thursday as weaker-than-expected U.S. manufacturing data and rising jobless claims dampened hopes of a demand rebound in the world's top energy consumer.

The U.S. manufacturing sector expanded in September, but missed analyst expectations, according a report from the Institute for Supply Management.

I really think the key was the manufacturing number... in spite of the fact that the consumer spending number was good, said Phil Flynn, PFGBest Research in Chicago.

A U.S. Labor Department report showed the number of U.S. workers seeking jobless benefits climbed last week.

The bleak economic data outweighed data showing that U.S. personal spending rose 1.3 percent in August in the largest gain since October 2001.

U.S. crude futures fell 49 cents to $70.12 a barrel by 2:00 p.m. EDT. The previous session saw a rise of nearly $4, the biggest daily jump in dollar terms since April.

London Brent crude dropped 50 cents to $68.57 a barrel.

A rare bilateral meeting between Western leaders and Iran in Geneva on Thursday may have also helped to ease oil prices.

This meeting is a good opportunity for fresh cooperation to remove international concerns, Tehran's chief nuclear negotiator Saeed Jalili said Thursday.

Iran's tensions with the West over the OPEC member's nuclear program have been a bullish factor in oil markets in recent years.

FUNDAMENTALS MIXED

The dip in oil prices followed a rally on Wednesday, which was spurred by data showing a drop in U.S. gasoline inventories -- a signal of increasing demand.

But analysts said it was too soon to talk of a strong upturn in demand and some expected prices to correct lower.

Aspects of the weekly petroleum report were supportive, at least relative to expectations, but the data was really a mixed affair, said Citi analyst Tim Evans in a research note.

To our eye, the rally looks very much overdone, with hot money simply chasing the price dynamically higher, he said.

Data from the U.S. government Energy Information Agency (EIA) showed a 1.6 million-barrel drop in gasoline stocks for the week ended September 25.

Distillates increased by 300,000 barrels to a 26-year high of 171.1 million, coming ahead of winter demand.

(Additional reporting by Robert Gibbons and Gene Ramos in New York, Emma Farge in London; Editing by Lisa Shumaker)

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