A Washington federal judge has set a showdown for Thursdaybetween Humana and the Federal Trade Commission overwhether the insurer will be forced to disclose documentsthe agency says it needs for its investigation of Walgreens Boots Alliance Inc.’s proposed $7billion acquisition of Rite Aid Corp.

Humana pushed back against an FTC subpoena demanding documentsthe agency has said will help it “understand the competitiveimpact” of the Walgreens-Rite Aid tie-up.

Humana, represented by the law firm Wiley Rein, argued that theFTC was asking for irrelevant documents and that the agency’sdemand would overly burden a company that is not directly involvedin the Walgreens-Rite Aid deal.

The FTC is not backing down.

In a rare “emergency petition” on Monday, the agency asked aWashington federal judge to enforce the subpoena—a push that couldsignal the agency is gearing up to challenge Walgreens and RiteAid’s merger plans.

U.S. Magistrate Judge G. Michael Harvey of the District ofColumbia has set a hearing for Thursday afternoon. A lawyer forHumana, Wiley Rein partner Richard Smith, co-chairman of the firm’slitigation group, declined to comment Tuesday.

The FTC said it needs the Humana records by June 26, noting thatWalgreens and Rite Aid could execute their deal—combining two ofthe three largest pharmacy chains in the country—as early as July7.

“Between now and then,” the agency said, regulators must decidewhether to challenge the deal as potentially anti-competitive. “Asa result, time is of the essence,” FTC lawyers wrote. “Any delay inthe resolution of the petition may limit the commission’s abilityto conduct a comprehensive evaluation of the transaction,” theagency lawyers said.

“Humana’s unexplained refusal to comply with the commission’ssubpoena hampers the commission’s ability to evaluate the proposedtransaction and determine what action is in the publicinterest.”

The FTC’s document request related to Humana’s Medicareprescription drug plans, which feature Wal-Mart as the preferredin-network pharmacy.

The subpoena also demanded the company’s communications with theCenters for Medicare and Medicaid Services “on seven broad topics,”Humana said last month in a petition to limit the documentrequests.

Humana challenged the subpoena as “a quintessential example of afishing expedition by the government for irrelevant documents, withthe full cost of that expedition being foisted upon Humana, anon-party.”

“The subpoena is grossly overbroad, and many of thespecifications are entirely unrelated to the FTC's investigation ofthe proposed acquisition,” Smith wrote in a filing on May 16 at theFederal Trade Commission. He added: “The costs that Humana, anon-party, will be forced to endure in an effort to isolate,collect, process, search for, review, and produce the documentsdemanded by the FTC are enormous, while the benefit to the FTC, ifany, is paltry.”

Humana’s lawyers are going back to the same court they campedout in for weeks not so long ago. A judge in January granted apreliminary injunction blocking Aetna Inc.’s proposed acquisition of Humana,prompting the companies to abandon their merger plans.