Oil slipped toward $65 a barrel, its lowest this month, on Monday as investors became more cautious about the pace of global economic recovery and any revival in energy demand.
The decline added to the market's $3.01, or 4.3 percent slide on Friday -- the biggest loss since July 29 -- after the Reuters/University of Michigan Survey of Consumers showed confidence in early August dropped.
It's a very weak market, continuing the weak tone on Friday, linked to falling stock markets and more bearish sentiment about demand, said Christopher Bellew, a broker at Bache Commodities.
U.S. crude oil futures for September fell $2.06 to $65.45 a barrel by 1340 GMT (9:40 a.m. EDT). Prices earlier hit an intra-day low of $65.32, the lowest since July 31. Brent crude for October lost $1.89 to $69.55.
Stocks in the United States opened lower, following on from losses in Europe and Asia <.EU>. The dollar rose against a basket of currencies.
U.S. stocks had been expected to open lower, even after a gauge of manufacturing in New York state moved into positive territory in August, suggesting growth in the sector for the first time since April 2008.
Oil's decline on Friday brought it to a weekly loss of 4.8 percent, snapping a four-week streak of gains that was largely fueled by optimism the global economy had turned a corner and recovery would boost energy demand.
Japan's economy emerged from its longest recession in at least 60 years in the second quarter, but analysts said it would be a long road to a sustained recovery in the world's third-largest oil consumer.
And while the Atlantic hurricane season, which can disrupt Gulf of Mexico oil and gas production, has arrived, analysts said brimming crude stockpiles in the United States would limit the impact of a storm on oil prices.
With Claudette downgraded to a tropical depression over southern Alabama, the energy market on Monday started to focus on Tropical Depression Ana as it moved toward Hispaniola, Cuba and Florida.
The U.S. National Hurricane Center did not expect much from Ana. The system will likely be a mere remnant of the depression when it reaches the Florida Panhandle later this week near where Claudette struck the coast.
Hurricane Bill was expected to spare the Caribbean Islands and the Gulf of Mexico as it targets Bermuda and the U.S. East Coast, the NHC and other weather models forecast.
(Reporting by Fayen Wong in Perth; Editing by Keiron Henderson)