"It is very bad for our Great Country.BUT WE ARE WINNING!"
Trump has long rallied against so-called "fake news", branding some of America's largest media outlets, including CNN and The New York Times, as such.
"This was a message, I believe, we were trying to communicate to the American people ... of a reminder of the importance of the free press, of the importance of what happens without a free press", she said. "Our reporters and editors strive for fairness".
Mr Trump has frequently criticised journalists and described news reports that contradict his opinion or policy positions as fake news.
In its editorial, the New York Times said it was correct to criticize the news media for underplaying or overplaying stories or for getting something wrong.
More than 300 newspapers have banded together to push back against US President Donald Trump's attacks on journalists. "But insisting that truths you don't like are "fake news" is unsafe to the lifeblood of democracy. They still do not understand why Donald Trump is the president of the United States". "I truly believe that America always solves its problems and combating unsafe and irresponsible attacks on journalism is no exception", Schumer said in a statement.
According to the Boston Globe, Thursday's participating newspapers are from big and small markets, including in states and counties where Trump won during the 2016 presidential election.
We're just not coordinating with other news organisations because the president's opinion, frankly, is not just that important to us.
The editorial board for the Capital Gazette in Annapolis wrote that the newspaper is more concerned with how its community sees it. "These attacks on the press are an attack on our nation's foundation".
Politico media writer Jack Shafer said the coordinated effort "is sure to backfire".
However, some newspapers decided not to run editorials on the issue, including The Washington Post.
"It will provide Trump with the circumstantial evidence of the existence of a national press cabal that has been convened exclusively to opposes him", he said.