Still, brokers admit they are puzzled by the resilience of the economy and the seemingly unbridled growth in demand, save for the small percentage of Americans who are trading in their SUVs or buying hybrid gas-electric vehicles.

"Once we're in this $55-$60 area, it's been kind of hard to justify," said oil analyst Andrew Lebow at Man Financial in New York. "But it is what it is. It seems like we'll hit $60 at this point."

But Lebow and other brokers said they remain on their toes, trying to anticipate some snippet of data that could augur a rapid decline in oil prices.

"Any reversal is going to be breathtaking when it happens," said oil broker Mike Fitzpatrick at Fimat USA in New York.

In London, Brent crude for August delivery settled 45 cents higher at $58.32 per barrel on the International Petroleum Exchange.

OPEC President Sheik Ahmed Fahd Al Ahmed Al Sabah said Monday that "if the prices continue to the end of this week at the same level, I will start consulting my colleagues to release the 500,000."

Last week the oil cartel agreed to raise its official production ceiling to 28 million barrels, starting July 1, but that failed to soothe traders because OPEC's output is already exceeding that level as producers seek to cash in on high prices. Including Iraq, which is not bound by the quota system, OPEC is pumping close to 30 million barrels a day, or about 35 percent of global demand.

Another development brokers were watching on Monday was the threat of a strike by oil workers in Norway, the world's third-largest exporter. A strike, which analysts said was unlikely, could begin as soon as Wednesday because of a salary dispute, potentially slicing the country's daily output of 3 million barrels by a third.

"If you take off 1 million barrels a day in this market, it's going to get ugly," said Bentz. "Let's just hope it doesn't happen."

While Nymex oil futures are more than 56 percent higher than a year ago, they are still below the inflation-adjusted high above $90 a barrel set in 1980.