United Parcel Service Inc. will begin Sunday pickup and delivery next year, joining competitor FedEx Corp., which announced the move to seven-day service in May.

The two largest U.S. couriers are under pressure to speed up deliveries as longtime customer Amazon.com Inc. morphs into a competitor by building out an overnight cargo-airline service, as well as a ground-delivery network.

UPS said the Sunday service would include SurePost, which are packages handed off to the U.S. Postal Service.

“Building on an expanded relationship with the Postal Service to help deliver seven-day service to our customers makes good business sense,” UPS Chief Marketing Officer, Kevin Warren said in a statement Tuesday.

A five-year union contract approved earlier this year created a new class of driver that gave UPS the flexibility to deliver on weekends. UPS said it’s also starting next-day ground delivery and adding more points for customers to drop-off and pick-up packages, including 6,000 CVS Health Corp. stores.