WASHINGTON (Reuters) - The Communication Workers of America labor union, which opposes T-Mobile’s proposed purchase of rival Sprint, has written to all 50 state attorneys general to highlight potential job losses from the proposed deal as well as antitrust concerns.

A sign for a T-Mobile store is seen in Manhattan, New York, U.S., April 30, 2018. REUTERS/Shannon Stapleton

Attorneys general in New York and California have reportedly begun probes into the $26 billion deal, which would see the third- and fourth-largest wireless carriers in the United States merging.

Utah and New Mexico have said they see the proposed transaction, announced in April, as positive because it will give the carriers a boost in building next generation 5G wireless technology and help them to extend into rural parts of the two states.

In the Sept. 10 letter from CWA President Christopher Shelton, a copy of which was sent to Reuters by the union, the CWA “expressed concern” about the deal and asked the attorneys general to investigate. The state attorneys general work with regulators and the federal government on deals they fear will cause harm locally.

The letter included a breakdown of the top 50 metropolitan areas that the union said were likely to see job losses because of the deal, mostly because of shuttered retail outlets. The CWA has estimated that the deal would lead to 28,000 lost jobs.

Shelton said the deal would “result in substantial harm to consumers and employees.”

T-Mobile declined comment on Friday. In testimony before Congress in June, T-Mobile chief executive John Legere said the combined company would hike overall employment, but acknowledged that there would be a reduction of 3,295 full-time retail jobs through 2024, along with other part-time and distributor job losses.

The CWA, which has 700,000 members, also said the deal would lead to increased concentration in the wireless industry, with four major competitors becoming just three. The union added that it was skeptical that the companies needed the deal to roll out 5G.

Debbie Goldman, the CWA’s telecommunications policy director, said the state attorneys general were in an “information-gathering period.”

The deal is being reviewed by the Justice Department and the Federal Communications Commission.