The US trade deficit shot up 10.4% in November to $47.75 billion after four consecutive months of declines, the commerce department said on Friday.
The gap between imports and exports reached its highest level in five months, while the increase in the deficit was the largest in percentage terms since May.
Analysts had forecast a November shortfall of $44.8 billion, up from $43.27 billion the previous month.
The unusually large trade deficit in November could push growth in the fourth quarter of 2011 below the 3.2% expected by most economists after gross domestic product expanded 1.8 % in the July-September period.
US exports of goods and services fell 0.85% in November to $177.84 billion, while imports rose 1.3% to $225.59 billion, the commerce department said.
The country's cumulative trade deficit for the first 11 months of last year was $512.78 billion, greater than the $500 billion registered for all of 2010.