The Department of Justice has subpoenaed New York Times journalists after they reported on security concerns involving the new, Qatari-gifted Air Force One, marking a dramatic escalation of President Donald Trump's campaign against the media that has drawn condemnation for eroding a fundamental freedom of American democracy.

The new jet, a present from the U.S. ally that the administration spent $400 million on to retrofit and upgrade, entered service last week. But Trump used an older model Air Force One jet to leave a NATO summit in Turkey and later referenced threats against him made by Iran.

The subpoenas seek to force the reporters to testify before a federal grand jury in Manhattan next week, the Times said, adding that federal agents delivered some subpoenas to the reporters at their homes. The subpoenas were issued after FBI Director Kash Patel and other Justice Department officials met at the White House on Friday to talk about the matter, according to a person familiar with the discussions who was not authorized to discuss the issue publicly and spoke on the condition of anonymity.

The Times journalists who received subpoenas included Julian E. Barnes, Eric Lipton, Tyler Pager and Eric Schmitt, the Times reported.

"The appearance of federal law enforcement agents on the doorstep of news reporters should shock the conscience of any American who believes in the Constitution and the press freedom it protects," David McCraw, a lawyer for the Times, said in a statement.

Bruce D. Brown, president of the Reporters Committee for Freedom of the Press, said Trump's "war on the press is looking for another victim."

He said in a statement that the subpoenas "break from longstanding Justice Department practice to protect the public interest and press independence by requiring prosecutors to only seek information from reporters as a last resort when all other avenues have been exhausted."

The department said that "to be clear, reporters are not the targets, those leaking classified information are."

Its statement said "we value and appreciate the important role that the press plays in this country, but DOJ also plays an important role to make sure that the people entrusted with our nation's secrets do what they're supposed to do with that information, which means not sharing classified information."

While recognizing "there may always be natural tension there," the department said "we are not going to ignore the law and stop investigating the people who work in the administration and think it's okay to leak classified information impacting national security."

Issuing subpoenas represents further ramping up of Trump's effort to threaten independent news organizations by leveraging the power of the federal government against them. It is also part of a systematic pattern by the Republican president to attempt to undermine press freedom in order to shield him from negative coverage.

Earlier this year, the Justice Department issued subpoenas seeking to compel testimony from reporters at The Washington Post and The Wall Street Journal. In both cases, the department later withdrew the subpoenas, though.

In January, FBI agents searched the home of Washington Post reporter Hannah Natanson, who has been covering Trump's transformation of the federal government, as part of a leak investigation into a Pentagon contractor accused of taking home classified information.

During his first term, Trump suggested that the press constituted an "enemy" of the American people. Since returning to the White House last year, he has waged an aggressive campaign against the media unlike any in modern U.S. history.