DEERFIELD, Ill. — Walgreen Co. will stay in Express Scripts Inc.’s pharmacy network for Blue Cross and Blue Shield of Kansas City and has offered continued access for the pharmacy benefit manager under the Department of Defense Tricare program.

Express Scripts customarily decides which pharmacies are in a health plan’s provider network, but a small number of its clients — including Blue Cross and Blue Shield of Kansas City — can choose for themselves. Walgreens and Express Scripts earlier agreed to let members of two health plans in Puerto Rico — MMM Healthcare Inc. and PMC Medicare Choice Inc. — maintain access to the chain’s pharmacies.

Walgreens announced in late June that it will leave Express Scripts’ retail pharmacy network after December 31 because of a contract impasse. The retailer and PBM remain at a standoff, and Walgreens has since begun efforts to move forward without participating in the Express Scripts network.

Walgreens says the terms it proposed to Express Scripts for Tricare, the U.S. military’s health benefits plan, would yield savings for the program without disrupting beneficiaries’ choice of a network pharmacy provider. The military is Express Scripts’ second-biggest client.

Published reports however, indicated that Express Scripts was unswayed by Walgreens’ latest offer.

Walgreens issued a statement last month saying it repeatedly offered to lower its rates and contract separately with Express Scripts for Tricare but that the PBM has declined to negotiate a separate pact for Tricare and its 6 million beneficiaries.

Walgreens said its latest proposal for Tricare includes “an ironclad guarantee” that the chain’s prices would match or beat the average cost per adjusted prescription of all other pharmacies in the network. “Those costs would be compared on an apples-to-apples basis and verified by an objective third party each quarter,” Walgreens stated, adding that it has committed to reimbursing Tricare for any overage after the end of each quarterly review.

In addition, Walgreens said that if it reaches an agreement with Express Scripts that includes lower rates than those proposed for Tricare, then Tricare would have the option to switch to those rates. The retailer noted that it had heard from nearly 200,000 Tricare beneficiaries who expressed concern about not having access to Walgreens pharmacies via the Express Scripts provider network.

Meanwhile, a second congressional panel will scrutinize Express Scripts’ planned acquisition of Medco Health Solutions Inc. The Senate Judiciary’s antitrust subcommittee will hold a hearing on the merger this month, following up a House subcommittee hearing in September.