Same-store sales were down from the previous quarter at the company's roughly 6,000 domestic units, nearly 30% of which are company owned. First-quarter same-store sales rose 3.8% for company-owned units and 3.7% at franchises during that period.

At company-owned locations, comparable sales rose 0.6% in April, 0.9% in May and 0.6% in June. Franchises were up 0.5% in April and May and flat in June. Management expects to release the full quarter's results on July 26.

The preliminary sales results come as the company is trying to sell itself. Nelson Peltz, the chairman of the company that owns the Arby's sandwich chain, wrote a letter earlier this week to Wendy's board saying that his firm, Triarc Cos., is a "natural, strategic" buyer for the company. Peltz, also a major Wendy's shareholder, also asked that a standstill agreement preventing Triarc from taking part in a potential acquisition be lifted.