Tribune Media, which has 44 television stations in 33 markets, had previously reached a deal with Sinclair Brodcasting but it was scuppered over FCC concerns

The US Department of Justice said Wednesday that Tribune Media and Nexstar must divest television stations in 13 markets to address concerns over their $6.4 billion merger.

The department's set the condition for the proposed merger between Nexstar, which owns 171 stations in 100 local markets and Tribune which holds 44 in 33 markets, according to DoJ figures.

The deal, announced in December, would create the largest operator of US local , reaching nearly 40 percent of households, overtaking competitor Sinclair Broadcasting which had previously tried to acquire Tribune.

Nexstar and Tribune will be required to divest one or more local channels in 13 markets, including Iowa, Michigan, Pennsylvania, Indiana, Alabama, Tennessee and Virginia.

"Without the required divestitures, Nexstar's merger with Tribune threatens significant competitive harm to cable and satellite TV subscribers and ," assistant attorney general Makan Delrahim said in a statement

The antitrust division feared the combined company "would likely charge cable and satellite companies higher retransmission fees ... resulting in higher monthly cable and satellite bills for millions of Americans."

It said the divestitures would address those concerns.

Tribune previously had reached a deal to be acquired by Sinclair, but the transaction died in August last year after the Federal Communications Commission balked at Sinclair's proposal to address market concentration concerns.