BERLIN (AP) - Commodities trader Glencore's net earnings fell 75 percent last year due to weaker sales prices and charges related to its holding in Russian aluminum maker UC Rusal, the company said Tuesday as it prepares to merge with mining company Xstrata PLC. Glencore reported full-year profit of $1 billion, down from the 2011 figure of $4.05 billion. It said one-time expenses came in at $1.21 billion, up from $511 million the previous year, due largely to impairment costs on its holding in Rusal. The company also booked a $128 million loss on disposal of investments after gaining $9 million the previous year. Revenue was up 15 percent to $214.4 billion from $186.2 billion a year earlier, due primarily to higher oil volumes. The Swiss-based company supplies raw materials such as oil, copper and wheat and owns plants, warehouses and mines. Glencore and Xstrata, the world's biggest exporter of thermal coal which also produces copper, nickel and zinc, agreed last year on a merger that would create an industry giant. Glencore said Tuesday that the so-called long stop date by which the merger, which still needs Chinese regulatory approval, has to be completed has been extended to April 16 from March 15. CEO Ivan Glasenberg said that the merged company will "incorporate the best of both businesses and plans to this effect are well advanced." Glasenberg noted in the company's report that 2012 was "a relatively lackluster year" for commodities, with average prices down 10 to 20 percent. However, he pointed to "signs of underlying economic improvement" in the U.S. and progress in China, including a smooth leadership transition, as hopeful signs. The company is proposing a 5 percent rise in its annual dividend to $0.1575, "reflecting our confidence in our business and the continued ramp-up of our brownfield industrial assets," Glasenberg wrote.