U.S. wholesalers increased their inventories sharply in December, the government reported Thursday, though gains are expected to slow in coming months, possibly limiting economic growth. The Commerce Department said wholesale inventories rose 1 percent in December after no gain the previous month. The rise came as sales at the wholesale level rose 1.3 percent, the best performance in nine months and more than double the 0.5 percent sales gain in November. The December gain pushed inventories to $473.9 billion, 22.5 percent above the lows seen in 2009. Strong inventory growth was a major factor supporting economic growth in the fourth quarter of 2011, but the trend is expected to flow in the early part of 2012, a major reason why economists expect slower overall growth in the current January-March period. Inventories at the wholesale level account for about a quarter of total business inventories. Supplies held by retailers comprise about one-third of the total, and manufacturing inventories represent about 40 percent of the total.