WASHINGTON — Customers might complain about the flood of unsolicited credit card applications, supermarket fliers and shopping catalogs in their mail, but the Postal Service is hoping to deliver even more.

Faced with multibillion-dollar losses and significant declines in first-class mail, the post office is cutting deals with businesses and direct mail marketers to increase the number of sales pitches they send by standard mail, the official term the agency uses for what is less kindly referred to as junk mail.

“Standard mail is the best way to reach your customer,” said Patrick R. Donahoe, the postmaster general, during a presentation last month on the future of the post office. “You can advertise on Facebook, but I don’t see how you can trace the number of ‘likes’ to return on investment.”

But as the Postal Service embraces direct mail to shore up its faltering bottom line, it faces opposition. Cities struggling to pay recycling and landfill costs to dispose of billions of pieces of unwanted mail are objecting to the expense. Localities estimate that they spend about $1 billion a year to collect and dispose of it.