SpaceX has agreed to acquire Grain Management's nationwide 800MHz spectrum portfolio.

While the financial terms of the deal weren't disclosed, The Wall Street Journal has reported that Elon Musk's company will pay $8 billion for the spectrum.

The spectrum will support SpaceX's ambitions to offer next-generation satellite direct-to-device (D2D) services for its Starlink Mobile service.

The transaction is subject to FCC approval and other customary closing conditions.

The acquisition comes a couple of days after SpaceX secured the go-ahead to deploy 15,000 high-capacity D2D satellites, as the company looks to compete with AT&T, Verizon, and T-Mobile.

Those three carriers notably formed a D2D satellite-focused spectrum-pooling joint venture (JV) last week.

SpaceX's Starlink Mobile already has existing access to 2GHz mid-band spectrum, which it's using to deliver high-capacity coverage in the US. The newly acquired low-band spectrum from Grain will enable its signal to pass through obstacles such as walls and extend service to devices indoors.

"For nearly twenty years, we have built Grain to see opportunity where others see complexity," said David Grain, founder and CEO, Grain Management. "Our spectrum expertise allows us to connect the strategic value of these assets with the technologies and operators that can realize their potential. This agreement with SpaceX brings that capability to bear at extraordinary scale, with the potential to change where and how Americans connect."

Grain only acquired the 800MHz airwaves back in August as part of a $2.9bn swap deal with T-Mobile, with the latter scooping up 600MHz frequencies from Grain as part of the exchange.

The spectrum was initially set to be picked up by EchoStar-owned Dish Network as part of an agreement with T-Mobile, when Dish was set to operate as the country's fourth mobile carrier. However, that deal fell through when Dish said it was unable to afford the spectrum.

Following the announcement yesterday (October 8), shares of AT&T, Verizon, and T-Mobile fell by around six percent in extended trading.