NEW YORK — A federal judge ruled today that The New York Times has a First Amendment privilege to protect the confidentiality of its sources by denying the government phone records in certain instances.

Saying that secrecy in government appears to be on the rise, Judge Robert W. Sweet refused to toss out a First Amendment lawsuit the newspaper filed last year to stop the Department of Justice from getting records of phone calls between two veteran journalists and sources.

"The free press has long performed an essential role in ensuring against abuses of governmental power," the judge said.

In the 120-page ruling, Sweet noted that the government can obtain telephone records during a grand jury investigation when the information sought is highly material and relevant and cannot be obtained elsewhere but he said those conditions had not been met.

"To deny the relief sought by the Times under these circumstances, without any showing on the part of the government that the sought records are necessary, relevant, material and unavailable from other sources, has the potential to significantly affect the reporting of news based upon information provided by confidential sources," Sweet wrote.

The government had sought records reflecting confidential communications between journalists Philip Shenon and Judith Miller and their sources from third parties that the newspaper said were unlikely to be interested in challenging its authority.

The Justice Department had advised the Times that it planned to obtain records of all telephone calls by Shenon and Miller for 20 days in the months immediately following the Sept. 11, 2001, terrorist attacks.

Times spokeswoman Catherine Mathis said, "We're very pleased with the ruling."

Megan L. Gaffney, a spokeswoman for federal prosecutors in Manhattan, said the office had no comment.

In his ruling, Sweet wrote: "The record before this court has demonstrated that the reporters at issue relied upon the promise of confidentiality to gather information concerning issues of paramount national importance — the nation's preparedness for the attacks of September 11, the government's efforts to combat al-Qaida post-September 11, and the risk posed to the American people by biological weapons.

"The government has failed to demonstrate that the balance of the competing interests weighs in its favor," he added.

The government had told the Times it wanted phone records from Shenon for a probe into a leak by a government employee about a planned raid on the offices of the Global Relief Foundation, an Islamic charity group accused of funding terrorist operations.

The Dec. 14, 2001, raid was not unexpected, and the newspaper had reported on Oct. 1, 2001, that the organization was suspected of providing money and support to terrorist operations, the Times said in its lawsuit. The suit added that neither Shenon nor the Times reported on the raid until after it occurred.

The lawsuit stated that Miller's phone records were being sought in connection with an investigation into an alleged leak from a government employee to Miller in late September and early October 2001. It said the alleged leak concerned a government decision to freeze the assets of the Global Relief Foundation and a Dallas-based Islamic charity, the Holy Land Foundation, which has been accused of aiding Hamas.

In a separate case, Miller is one of two reporters facing jail for refusing to divulge their sources about the 2003 leak of an undercover CIA officer's name. The other is Matthew Cooper of Time magazine.