Oil fell after another big weekly build-up in the United States, crude inventories and a possible rise in Saudi output stoked worries about oversupply. According to analysts, production by Saudi Arabia, the world's biggest exporter, may be increasing to nearly 10 million barrels per day. U.S. crude was down 2.10 dollars, at 50.04 dollars a barrel. Brent crude oil futures slipped 1.52 dollars, to 59.01 dollars a barrel, extending the decline from Tuesday's two-month high of 63 dollars a barrel.