WASHINGTON (Reuters) - Wholesale inventories rose as expected in August while sales at wholesalers posted the first gain in four months, government data released on Wednesday showed.

Total wholesale inventories gained 0.5 percent to $487.5 billion, the Commerce Department said.

Economists polled by Reuters had expected stocks of unsold goods at U.S. wholesalers to rise 0.5 percent after advancing by 0.6 percent in July, which was revised down from a previously reported 0.7 percent gain.

Inventories are a key element in the government's measure of changes in gross domestic product and can highlight underlying strength or weakness in U.S. growth, which notched a 1.3 percent annual pace in the second quarter.

In August, automobile inventories were unchanged and computer equipment stocks fell 5.1 percent, while machinery increased 1.7 percent.

Sales at wholesalers rose 0.9 percent, the first increase since April. Economists had expected sales up by 0.5 percent.

Sales gains in August were widespread, with furniture up by 1.1 percent and machinery advancing 0.5 percent. Petroleum sales rose 5.6 percent and auto sales were up by 2 percent.

At August's sales pace it would take 1.20 months to clear shelves, down slightly from 1.21 months in July.

(Reporting by Alister Bull; Editing by Neil Stempleman)