(Bloomberg) — United Parcel Service Inc. expects to cut 20,000 jobs this year and close dozens of facilities as it dramatically reduces shipments for e-commerce giant Amazon.com Inc.

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The reduction in its operational workforce — a group that includes delivery drivers and package handlers — is part of a network overhaul in response to expected “lower volumes from our largest customer,” UPS said Tuesday. The Atlanta-based company will shutter 73 leased and owned buildings by the end of June and said it may identify additional facilities for closure.

UPS aims to cut expenses and improve profitability after announcing a plan in January to slash the number of low-margin Amazon parcels it delivers by more than half over 18 months. The network reconfiguration is expected to generate $3.5 billion of total cost savings this year.

Amazon said in an emailed statement that UPS requested a reduction in volume “due to their operational needs.” Amazon will “continue to partner with them and many other carriers to serve our customers.”

UPS has about 490,000 employees, suggesting the planned contraction will account for 4% of its staff. Last year it announced 12,000 management job cuts.

The latest move drew condemnation from the Teamsters union, which represents about 300,000 UPS workers. Sean O’Brien, the organization’s general president, said the company is contractually obligated to create 30,000 jobs.

“If UPS wants to continue to downsize corporate management, the Teamsters won’t stand in its way,” he said in a statement. “But if the company intends to violate our contract or makes any attempt to go after hard-fought, good-paying Teamsters jobs, UPS will be in for a hell of a fight.”

The courier has sought greater efficiency in the face of a decline in volumes following a pandemic-driven boom in e-commerce. The industry is also grappling with new challenges from President Donald Trump’s tariffs, which have complicated cross-border goods shipments and injected volatility into the global economy. UPS on Tuesday backed away from its 2025 financial guidance, saying it wouldn’t provide an update “given the current macroeconomic uncertainty.”

Still, the company reported adjusted earnings of $1.49 a share for the first three months of the year, topping the $1.40 average of analyst estimates compiled by Bloomberg. Revenue in the quarter also narrowly beat expectations.