NEW YORK (Reuters) - Oil prices fell from fresh 21-year highs on Wednesday, after U.S. gasoline supplies jumped and the president of production cartel OPEC said the group could immediately boost output to help cool prices, reversing previous statements.

Beleaguered Russian oil giant Yukos assured analysts it would be free to use its bank accounts to keep exports flowing, which also pushed down prices.

U.S. crude settled $1.32 lower at $42.83 a barrel, after soaring to $44.34 in overnight trade, the highest since oil futures were launched on the New York Mercantile Exchange in 1983.

Brent crude fell 94 cents to $39.70 a barrel, easing from a record high earlier of $40.99. That was the highest level since London's International Petroleum Exchange launched trading in Brent futures in 1988.

Oil prices have risen by more than one-third since the end of 2003 on worries that accelerating global demand has left supplies tightly stretched with little leeway for disruption.

Organization of the Petroleum Exporting Countries (OPEC) President Purnomo Yusgaintoro, who is also Indonesia's oil minister, said on Wednesday the cartel was concerned about high oil prices and could immediately tap into its 1 million to 1.5 million barrels per day of spare production capacity.

Wednesday's statement came a day after Purnomo said the group could not pump any more crude to cool prices. He also said that Saudi Arabia, the world's biggest exporter, had spare production capacity, but it could not raise output immediately.

In recent weeks, oil prices have also been rallying due to troubles in non-OPEC Russia, the world's second-largest oil exporter. The Kremlin has demanded that Yukos, Russia's largest oil company, pay billions of dollars in taxes for the year 2000.

But Yukos officials said Wednesday that bailiffs had informed them it could use its bank accounts to finance core operations, a move aimed at alleviating fears over possible disruptions to the company's exports.

In its weekly data, the U.S. Energy Information Agency said gasoline stocks rose 2.4 million barrels last week to 210.1 million barrels. Analysts had expected stocks to fall 600,000 barrels due to peak summer demand from vacation drivers.

U.S. distillate stocks rose 2.1 million barrels, above analysts' expectations for a rise of 1.4 million barrels.

Gasoline demand over the past four weeks was down 0.3 percent on the year, a reversal of strong demand growth that took U.S. gasoline futures to record highs in May and helped push crude prices higher.

"It's a bad report for products," said Kyle Cooper, analyst at Citigroup Global Markets. "We now are 8.3 million barrels above last year in terms of gasoline, and yet we are 50 percent higher in terms of price. I'd like someone to explain that to me."

U.S. gasoline futures fell 3.36 cents, or 2.6 percent, to $1.2530 a gallon.

Consistently high crude oil prices are fanning concern that energy costs are hurting global economic expansion.

"The oil price is, of course, a concern," said German Finance Minister Hans Eichel. "It could slow economic growth."

Allowing for inflation, prices are near the level hit during the 1973 oil embargo and just over half those during the oil price shock following the 1979 Iranian revolution.

Some wider impact has already been felt. U.S. consumer spending in Junefell at the fastest rate since September 2001, according to U.S. government data released on Tuesday. High oil prices contributed to the fall as consumers cut back on new vehicle purchases.

However, the evidence of further damage to world economies remains patchy. U.S. consumer confidence climbed last week, and figures from U.S. automakers show vehicle sales in the world's largest energy consumer registered robust gains in July.

But analysts warned that rising prices are set to damage expanding economies that rely on oil imports, such as India, Asia's fourth-largest economy, which imports 70 percent of its crude oil requirements.