T-Mobile US Inc. (TMUS.O) won U.S. national security approval for its takeover of Sprint Corp., according to two people familiar with the matter, one of the regulatory conditions needed before the two wireless carriers can combine.

The Committee on Foreign Investment in the U.S., or Cfius, has notified the companies that it was clearing the deal, said the people, who weren’t authorized to speak publicly about the review.

The approval moves the No. 3 and No. 4 wireless providers in the U.S. closer to consummating their US$26.5 billion tie-up in a bid to better compete against industry leaders AT&T Inc. (T.N) and Verizon Communications Inc (VZ.N). Their focus now shifts to securing approval from Federal Communications Commission and the Justice Department’s antitrust division.

T-Mobile and Sprint declined to comment.

Cfius is reviewing the deal because T-Mobile and Sprint are owned by foreign companies: Deutsche Telekom AG, the parent of T-Mobile, and SoftBank Group Corp., which owns Sprint. Deutsche Telekom, based in Bonn, would own 42 per cent of the new company, while Tokyo-based SoftBank would own 27 per cent.

Bloomberg News reported Friday that the carriers had an agreement in principle with Cfius, with final details still to be worked out.

Cfius, which is led by the Treasury Department, is tasked with ensuring that foreign investment in American companies doesn’t pose risks to national security. It pays particular attention to deals involving critical infrastructure like wireless networks.