Six Democratic senators urged the U.S. Federal Communications Commission and the U.S. Department of Justice to reject the proposed merger between T-Mobile US Inc. and Sprint Corp.

In a May 23 letter to FCC Chairman Ajit Pai and Assistant Attorney General Makan Delrahim, the U.S. senators raised concerns that the merger will not serve the public interest and would result in "substantial anticompetitive effects, harming consumers, workers, and innovation." They also asked regulators to open a 30-day public comment period on the matter.

The senators argued that the conditions and voluntary commitments offered by the companies to address regulatory concerns are "insufficient."

T-Mobile said May 20 that it submitted a set of commitments to the FCC in connection with the pending deal, which included timelines around the deployment of next-generation 5G service as well as a pledge to divest Sprint's Boost Mobile prepaid brand.

Bloomberg News recently reported that the DOJ is leaning toward rejecting the pending merger between T-Mobile and Sprint, as the concessions do not satisfy the department's antitrust concerns.

The senators who have signed the letter are Tom Udall, D-N.M.; Richard Blumenthal, D-Conn.; Amy Klobuchar, D-Minn.; Elizabeth Warren, D-Mass.; Edward Markey, D-Mass.; and Cory Booker, D-N.J.