WASHINGTON – The nearly bankrupt U.S. Postal Service is moving forward with a multibillion-dollar cost-cutting plan that will close nearly 250 mail processing centers, saying Thursday it can no longer wait as Congress remains deadlocked over how to help.

At a news briefing, Postmaster General Patrick Donahoe said the agency’s mail processing network had simply become too big, given declining first-class mail volume and mounting debt. It will now consolidate nearly 250 plants as originally proposed, including 48 this summer, but will stretch out the remainder over a longer time frame in 2013 and 2014.

Nearly half the Senate had written letters to Donahoe asking that he hold off on closing any mail facility until Congress could pass final postal overhaul legislation.

Under the modified approach, up to 140 processing centers will be consolidated by February — roughly 48 in August and about 90 in January and February. Closings would be suspended during the Postal Service’s busy election and holiday mail seasons. Another 89 closings would occur in 2014.