Top office products retailer Staples Inc on Tuesday reported a 38 percent drop in quarterly profit as costs increased.

Staples, which refrained from providing any sales or earnings outlook, however reaffirmed its expectations for synergies related to its Corporate Express acquisition.

The company, which bought Dutch rival Corporate Express in July last year, said it still expected to save up to $300 million annually over the three-year integration period.

Net earnings fell to $92.4 million, or 13 cents a share, in the second quarter that ended on August 1, from $150.2 million, or 21 cents a share, a year earlier.

Excluding a pretax integration and restructuring charge of $30 million, Staples earned 16 cents a share, in line with the average Wall Street forecast, according to Reuters Estimates.

Staples, which is poised to gain from any recovery in corporate spending with its acquisition of Corporate Express, said in July that it was seeing a rebound at its North American delivery unit that serves small businesses.

While sales rose 9 percent to $5.5 billion, both operating expenses and costs of goods sold increased in the quarter.

North American retail sales fell 5 percent to $2 billion as sales at existing stores fell 5 percent, reflecting declines in average order size and weakness in durable goods such as business machines and furniture.

The U.S. recession has hurt office supplies retailers hard as consumers and small businesses curtail their appetites for nonessential goods, especially big-ticket items like furniture and computers.

Last month, Staples' rivals OfficeMax Inc and Office Depot gave lackluster outlooks for the rest of the year as they forecast economic woes continuing to weigh on sales and expected a soft back-to-school season.

Staples shares, which have risen about 26 percent since the start of 2009, were unchanged before the opening bell.

(Reporting by Dhanya Skariachan; Editing by Lisa Von Ahn and Maureen Bavdek)