U.S. wholesalers increased their stockpiles modestly in March, but by less than economists had expected, as the value of petroleum stockpiles dropped by the most in nearly two years.

Wholesale inventories increased 0.3 percent to $480.44 billion, compared with a 0.6 percent gain estimated by economists, the Commerce Department said Wednesday. February's initial reading of a 0.9 percent gain was unrevised.

Stockpiles of nondurable goods fell 0.6 percent from February, dragged down by a 5.9 percent decline in petroleum stockpiles and a 2 percent drop in paper products.

Inventories of durable goods, such as machinery, automobiles and furniture, increased 1 percent in March, the new report showed, after a 0.6 percent increase in February.

Sales at wholesalers climbed 0.5 percent in March, on the back of a downwardly revised 1.1 percent increase in February but below economists' expectations of a 0.7 percent increase.

Enough goods were kept on hand by the wholesalers to last 1.17 months at the current sales pace in March, the same as in February.

Separately, the latest Institute for Supply Management manufacturing report indicated a slight contraction in stockpiles in April. Wholesalers make up about 30 percent of all business stockpiles.