WASHINGTON (Reuters) - Twelve U.S. senators on Thursday asked the Federal Communications Commission to investigate Sinclair Broadcasting Group SBGI.O for "deliberately distorting news" and asked the commission to pause its ongoing review of the company's proposed $3.9 billion acquisition of Tribune Media Co TRCO.N.

The Federal Communications Commission (FCC) logo is seen before the FCC Net Neutrality hearing in Washington February 26, 2015. REUTERS/Yuri Gripas

Sinclair, which is already the largest U.S. broadcaststation owner, announced plans in May 2017 to acquire Tribune’s 42 TV stations in 33 markets, extending its reach to 72 percent of American households.

In a letter, the senators, 11 Democrats and independent Bernie Sanders, expressed concern about local news anchors at Sinclair-owned stations around the country being forced to read company-mandated scripts. The scripts criticized “the troubling trend of irresponsible, one sided news stories plaguing our country” and have drawn fire.

“We are concerned that Sinclair is engaged in a systematic news distortion operation that seeks to undermine freedom of the press and the robust localism and diversity of viewpoint that is the foundation of our national broadcasting laws,” the senators wrote. They added that it “may have violated the FCC’s longstanding policy against broadcast licensees deliberately distorting news by staging, slanting, or falsifying information.”

In a letter to senators on Thursday reviewed by Reuters, FCC Chairman Ajit Pai rejected their request, saying the agency does not have authority to revoke a license based on the content of a particular newscast. Pai made similar comments last year when President Donald Trump suggested NBC’s licenses could be challenged over its news reporting.

“I can hardly think of an action more chilling of free speech than the federal government investigating a broadcast station because of disagreement with its news coverage or promotion of that coverage,” Pai wrote.

After the scripts drew significant public attention, Trump tweeted on April 2 in defense of Sinclair: “Sinclair is far superior to CNN and even more Fake NBC.”

In February, Representative Frank Pallone, a Democrat, said the FCC’s inspector general was investigating whether Pai was biased in Sinclair’s favor.

Pallone in November asked the inspector general to investigate, citing a string of FCC decisions he said benefited Sinclair and a media report that Trump’s election campaign struck a deal with Sinclair for favorable coverage.

Pai has repeatedly denied he has taken actions aimed at benefiting a single company and Sinclair has denied improper conduct.

Sinclair declined to comment on the senators’ letter, signed by the 11 Democrats, including Senators Maria Cantwell, Tom Udall, Elizabeth Warren, Cory Booker and Richard Blumenthal, as well as Sanders.