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The Department of Justice may be preparing to move on T-Mobile's merger with Sprint, and the companies' subsequent side deal with Dish over Sprint's divested assets.

In a report on Thursday, CNBC's David Faber says that the deal has reached its "decision days," which would have the DOJ approve T-Mobile's $26.5 billion merger with Sprint and then see Dish acquire divested Sprint assets and become a fourth wireless carrier.

As part of the deal, T-Mobile would reportedly allow Dish to fully use its network for three years while Dish builds out its own wireless network using the billions of dollars of wireless spectrum the satellite provider has acquired over the years. After three years Dish's wireless business will be gradually weaned off of T-Mobile's network, according to the report.

T-Mobile, Sprint latest: If the parties do not settle next week, the Justice Dept. would sue to block the merger, sources say. But optimism remains that the parties could settle. (via @DavidFaber) pic.twitter.com/LAStqrTHpK — CNBC Now (@CNBCnow) July 18, 2019

Faber says that T-Mobile parent Deutsche Telekom will need to make a decision next week on if it will allow a different company to be able to buy Dish in the future. Deutsche Telekom wants the network sharing deal to expire if Dish is acquired by a cable company, something that the DOJ is reportedly objecting to.

If Deutsche Telekom doesn't agree to the DOJ's terms, which would allow a cable company to buy Dish during this period without losing access to T-Mobile's network, the department's antitrust division will sue next week to block the deal, according to Faber. Over a dozen state attorneys general are currently suing to block the deal.

Even with its billions of dollars in spectrum holdings, the large investment needed to build out a nationwide wireless network has led to rumors that Dish would need a partner for its wireless business.

It also has made Dish a potential acquisition target by a cable company such as Comcast or Charter, both of which have already been experimenting in wireless with their respective Xfinity Mobile and Spectrum Mobile offerings.

T-Mobile and Sprint were already facing a July 29 deadline for their merger (though a recent Wall Street Journal report suggested it might be extended). Dish faces a March 2020 deadline by the Federal Communications Commission to have a network that satisfies the FCC's deployment requirements or risk losing its spectrum.

T-Mobile and Dish declined to comment when asked about the new report. The Department of Justice didn't immediately respond to a request for comment.