CBS’ TV stations are raising some questions about Comcast’s $30 billion deal for NBC Universal and suggesting they could carry those doubts to federal regulators.

In a letter sent Tuesday to CBS affiliates, Tim Busch, chairman of the CBS Television Network Affiliates Association, warned its members that the affiliate association board is worried that the deal could disadvantage CBS stations.

“We are concerned that the proposed merger would competitively disadvantage CBS affiliates by reposing an unprecedented level of media market power in a single vertically integrated cable/television broadcast network company,” Busch wrote.

Busch said the CBS affiliate board has conferred with the Fox and ABC affiliate associations about communicating joint concerns to the Federal Communications Commission, which, along with the Justice Department, is reviewing the deal.

And, he said, the affiliate group has asked for a meeting with Comcast in the hopes that Comcast “will voluntarily agree to have certain regulatory conditions incorporated into any FCC approval of the merger to assure nondiscriminatory and fair treatment of CBS-affiliated stations following the merger.”

 “Our specific concern is that Comcast/NBCU would have incentives to competitively disadvantage and discriminate against non-NBC-affiliated stations in terms of Comcast’s cable carriage, retransmission consent negotiations, and advertising and promotion practices.”

Busch didn’t return a call from TheWrap for comment.

Broadcasting observers say Comcast’s deal for NBC Universal poses several potential problems for rival broadcasters. Rivals may want assurances that Comcast won’t move their stations to lesser cable dial positions or otherwise treat their stations differently than NBC stations.

There is also concern that Comcast ownership of NBC Universal would let Comcast take a tougher approach in negotiations with rivals for local station retransmission fees, because any disputes could wind up benefitting NBC stations.

Neither Comcast nor NBC Universal immediately returned a request for comment on the letter.

While the Justice Department has been talking to individuals and groups about the deal, the FCC is seeking public comments.

Initial comments have to be filed with the FCC by May 3. Then, everybody gets until June 2 to respond to the initial comments. Finally, responses to the responses have to be in by June 17.

The FCC last week rejected an attempt by consumer groups to extend the comment period.