Verizon may be close to sealing its spectrum deal with major cable companies, say sources close to the company’s negotiations with the U.S. Department of Justice and the Federal Communications Commission.

The DOJ and FCC are currently vetting the purchase, and the Justice Department’s Antitrust Division is likely to place some strict conditions on the arrangement, according to three anonymous sources who spoke to Reuters. The department “had significant concerns about the anticompetitive potential of key features of the proposed agreement,” one of the sources said.

Verizon first announced its intention to buy the spectrum in December. The acquisition includes 122 wireless services licenses from Comcast, Time Warner Cable, and Bright House Networks.

While the extra spectrum would allow Verizon to give its wireless customers faster data service, the matter has stirred up quite a bit of controversy among Verizon’s competitors. T-Mobile, for example, asked the DOJ to kill the deal altogether back in February, arguing that allowing the deal to go through would give Verizon an “excessive concentration” of spectrum, which in turn could stifle competition.

Antitrust regulators have some of the same concerns, especially around Verizon and Comcast cross-marketing each other’s products. In the adjusted deal, FiOS cross-marketing in particular would be prohibited.

The DOJ has been probing the acquisition since it was announced in December 2011. The spectrum Verizon is trying to buy was originally licensed by the government to promote additional competition in the wireless service market.