According to Bloomberg, the US Department of Justice has just announced that it will submit a deferment request for the Sprint / Softbank merger to the FCC. Telecom acquisitions in the United States require approval from both the DoJ and the FCC, with the former agency focusing largely on potential anti-trust issues. Softbank officially announced the buyout in October.
It's not exactly a big surprise that the DoJ is looking at this deal cautiously. After the failure of the AT&T / T-Mobile merger for potential anti-trust and consumer protection concerns, the DoJ likely feels compelled to investigate a foreign takeover of a major US telecom with extra care. This isn't necessarily indicative of a problem, though the DoJ
did not comment specifically on the reasoning behind the request for more time has cited "national security concerns" as the reason for extended review.
Sprint can't be happy about this, as the review will only serve to delay much-needed funds Softbank was planning to pump into the indebted wireless provider's LTE network buildout.