The U.S. trade deficit widened in December for a second month as the cost of imported oil climbed to the highest level in two years.

The gap grew 5.9 percent to $40.6 billion, in line with the $40.5 billion median forecast in a Bloomberg survey of economists, Commerce Department data showed today in Washington. Excluding petroleum, the shortfall shrank to $15.3 billion, the smallest since March.

For all of 2010, the trade gap surged 43 percent, the biggest jump in a decade, as the recovery in spending led to record imports of consumer goods. At the same time, manufacturers like Caterpillar Inc. benefited from a drop in the value of the dollar that drove the biggest annual increase in exports in two decades, capped by record demand in December from China and newly industrialized Asian nations.

“U.S. consumers went on a tear at the end of the year,” Chris Rupkey, chief financial economist at Bank of Tokyo- Mitsubishi UFJ Ltd. in New York, said before the report. “U.S. manufacturers are doing well in world markets and are priced well vis-à-vis the dollar.”

The trade gap was projected to widen, according to the median forecast of 77 economists surveyed. Estimates ranged from deficits of $37.4 billion to $43.5 billion. The Commerce Department didn’t revise the November shortfall of $38.3 billion.

The trade gap climbed to $497.8 billion in 2010 from $374.9 billion the prior year. The shortfall was still below the $698.8 billion shortfall registered in 2008.

Effect on Growth

After eliminating the influence of prices, which are the numbers used to calculate gross domestic product, the trade deficit increased in December to $46 billion from $45.2 billion.

Imports rose 2.6 percent to $203.5 billion, the most since October 2008. The value of crude oil purchases increased to $22.5 billion from $19.8 billion. The average price per barrel of imported crude reached $79.78, the highest since October 2008.

American households have contributed more to the recovery in recent months, propelling the gain in demand for foreign goods. Consumer spending, which accounts for 70 percent of the economy, rose at a 4.4 percent annual pace in the fourth quarter, the biggest gain in four years, according to Commerce Department figures.

The gain in imports is supplementing improving sales overseas. China, set to become the world’s second-largest economy this year, expanded 9.8 percent in the fourth quarter from a year earlier. India grew 8.9 percent in the third quarter and Brazil, South America’s largest economy, advanced 6.7 percent.

Growing Exports

Exports increased 1.8 percent to $163 billion, the most since July 2008, led by sales of autos, chemicals and industrial machines.

Caterpillar, the world’s largest maker of construction equipment, posted fourth-quarter profit that topped analysts’ estimates as sales advanced in China, Australia and Latin America. The Peoria, Illinois-based company said 2011 sales will top $50 billion after coming in at $42.6 billion last year.

“Sales are improving in every region, and are at or near records in the developing world,” Mike DeWalt, director of investor relations at Caterpillar, said on a Jan. 27 teleconference. “Over the past quarter, we’ve become somewhat more positive about economic growth in the developed economies of North America, Europe, and Japan.”

The U.S. trade gap with China narrowed to $20.7 billion in December from $25.6 billion the prior month. Demand for American goods from countries in the European Union climbed to the highest level since October 2008.

Dollar’s Drop

Since reaching a one-year high on June 7, the dollar has dropped 8.1 percent through yesterday against a trade-weighted basket of currencies. The decrease makes American goods cheaper to buyers abroad and will keep spurring manufacturing, which expanded for an 18th consecutive month in January.

President Barack Obama, who has set a goal of doubling American exports by 2014, said last month in his State of the Union address that the U.S. has made progress.

“Already, our exports are up,” Obama said Jan. 25. “Recently, we signed agreements with India and China that will support more than 250,000 jobs here in the United States. And last month, we finalized a trade agreement with South Korea that will support at least 70,000 American jobs.”