FedEx Corp. has agreed to acquire ShopRunner, an e-commerce service that provides shipping for more than 100 brands, as the courier seeks to deepen its ties with online shoppers.

ShopRunner will operate as a subsidiary of FedEx Services once the deal is complete, the delivery giant said in a statement. FedEx didn’t provide financial terms of the transaction, which is expected to close by yearend.

The acquisition tightens FedEx’s embrace of surging e-commerce deliveries, adding to earlier moves such as adopting seven-day service and investing in handling large residential packages. ShopRunner allows online shoppers to choose its two-day shipping and free returns service for brands including Bloomingdale’s, Saks Fifth Avenue and Under Armour.

The deal is part of FedEx’s “continued efforts to create an open, collaborative e-commerce ecosystem that helps merchants deliver seamless experiences for their customers,” said Chief Operating Officer Raj Subramaniam.

In the three-month period ending Aug. 31, sales at FedEx’s U.S. ground-delivery unit jumped 36% to $7 billion from a year earlier.

The purchase of ShopRunner “should help it further penetrate” the e-commerce market, Allison Landry, an analyst with Credit Suisse Group AG, said in a note to clients.