(Reuters) – United Parcel Service Inc on Thursday said accelerated spending on weekend deliveries and speedier service would take a bite out of 2020 earnings, sending shares down almost 5 percent in midday trading.

UPS is racing to wring more profit from booming e-commerce shipments, which are forcing the company and rivals like FedEx Corp to make significant strategy shifts.

UPS shares were down $5.46 to $110.30 in midday trading.

The Atlanta-based company forecast adjusted earnings of $7.76 to $8.06 per share – a penny below analysts’ average estimate, according to IBES data from Refinitiv.

The world’s biggest package delivery firm this year is pulling forward projects to cater to always-on online retailers. That includes its plan to double weekend deliveries in the United States.

UPS is supporting that effort with extended package pickup hours for retailers who ship online orders from their stores. It is also hiring weekend delivery drivers, Friday night sortation workers and overnight semitruck “sleeper teams” that get packages to hubs more quickly.

“The investments are going to be accretive in 2021. There is a short-term return on this,” UPS Chief Executive David Abney told Reuters.

U.S. operations outperformed international during the fourth quarter, when the company’s profit of $2.11 per share matched Wall Street’s target despite a slight miss on revenue.

Network efficiency and the addition of new airplanes boosted results in the company’s core domestic unit.

U.S. revenue grew more than 6.5% and operating margin ticked higher, helped by a 2.1% decline in cost per unit.

Amazon.com Inc, UPS’s largest customer, drove domestic results in the quarter that included the all-important holiday season.

That helped fuel worries that UPS is too dependent on Amazon, which is building a competing logistics operation.

The world’s leading online retailer accounts for about 10% of UPS revenue and delivered 3.5 billion of its own packages last year.

International revenue at UPS fell 1.7% in the quarter. That unit’s margins improved slightly more than expected, despite a slight revenue shortfall, Cowen analyst Helane Becker said in a client note.