(Recasts lead, adds further quotes , reaction from Democratic senator)
WASHINGTON, Oct 17 (Reuters) - The top U.S. communications regulator on Tuesday dismissed President Donald Trump's suggestion the NBC network's broadcast licenses could be pulled after it ran stories Trump declared untrue, saying "the FCC under my leadership will stand for the First Amendment."
Ajit Pai, a Republican who was named chairman of the Federal Communications Commission by Trump in January, broke days of silence by rejecting Trump's tweet last week asserting the FCC could challenge the license of NBC after stories Trump declared were not true.
"Under the law, the FCC does not have the authority to revoke a license of a broadcast station based on the content of a particular newscast," Pai said at a forum in Washington. "I believe in the First Amendment. The FCC under my leadership will stand for the First Amendment."
The First Amendment of the U.S. Constitution guarantees freedom of speech and freedom of the press.
Democrats had been pushing Pai to denounce Trump's suggestion that broadcast licenses could be threatened following reports by NBC News that his secretary of state, Rex Tillerson, had called him a "moron" after a discussion of the U.S. nuclear arsenal.
But Pai did not criticize Trump by name and did not talk to reporters after the event. It was similar to a prior episode in which Pai said he did not agree with Trump's contention that the media was the "enemy of the people."
Last Wednesday, Trump tweeted, "With all of the Fake News coming out of NBC and the Networks, at what point is it appropriate to challenge their License? Bad for country!"
Trump and his supporters have repeatedly used the term "fake news" to cast doubt on media reports critical of his administration, often without providing any evidence to support their case that the reports were untrue.
Pai was asked Tuesday if the FCC has any role in determining what constitutes "fake news." Pai said "traditionally that has not been within the FCC jurisdiction."
Democratic U.S. Senator Brian Schatz said Pai's "statement is better than nothing, but it is merely a reiteration of the FCC's authorities under the law. What we needed is a full-throated defense of the independence of the FCC against political interference."
Any move to challenge media companies' licenses, however, would likely face significant hurdles.
The FCC, an independent federal agency, does not license broadcast networks, but issues them to individual broadcast stations that are renewed on a staggered basis for eight-year periods.
Comcast Corp, which owns NBC Universal, also owns 11 broadcast stations, including outlets in New York, Washington, Los Angeles, San Francisco, Boston, Dallas and Chicago.
When reviewing licenses the FCC must determine if a renewal is in the public interest. Courts have held that a station exercising its First Amendment rights is not adequate grounds to challenge a license.
The agency does not issue similar licenses for cable networks such as CNN and MSNBC, or regulate internet news or other websites.
In the early 1970s, then-President Richard Nixon and his top aides discussed using the FCC's license renewal process as a way of punishing The Washington Post for its coverage of the Watergate burglary that ultimately brought down his presidency. (Reporting by David Shepardson; Editing by Chris Sanders and Jonathan Oatis)