The U.S. Postal Service announced on Thursday new plans to consolidate or close 223 mail processing plants, putting 35,000 jobs at stake starting in late May or June, CNNMoney reported.

The move would save $2.1 billion and is part of the agency’s broader effort to save $20 billion in the next three years.

The Postal Service is in debt due to declining first-class mail volume and a congressional mandate to prefund retirement health-care benefits.

The plant consolidations are the latest in an array of controversial cost-cutting measures under consideration at the Postal Service. Also on the table are slashing Saturday service,delaying delivery of some first-class mail, closing post offices and hiking the price of a first-class stamp by a nickel to 50 cents.

The Postal Service says that it faces $18 billion in losses by 2015 if nothing is done.