A leading reporter on the national security beat, William Gertz of the Washington Times, has been ordered to appear before a federal judge next month to identify the sources for a news article about the prosecution of a Chinese spy ring based in southern California.

Judge Cormac Carney, who sits in Santa Ana, Calif., has subpoenaed Mr. Gertz to testify on June 13 about his sources for a 2006 story in which he described new charges expected to be filed against an engineer who worked for American defense contractors, Chi Mak, as well as several of his relatives. New indictments were filed in the case, largely, but not entirely, as the article predicted.

Mr. Gertz did not respond to an e-mail message last night seeking comment.

A law professor who specializes in disputes involving the press said the case could escalate into a major First Amendment showdown with the prospect of jail time or large fines for Mr. Gertz.

“I think it’s very unlikely he’s going to go in there and say, ‘Okay, I’ll tell you who it is.’ I’m sure he’ll go to the mat for it,” Jane Kirtley of the University of Minnesota said.

There are signs Mr. Gertz plans to resist the subpoena. Court records show that last week, two Washington-based lawyers, Allen Farber and Charles Leeper, filed paperwork to appear on the reporter’s behalf. The attorneys, who are part of a Philadelphia-based firm, Drinker Biddle, did not return messages last night seeking comment for this article.

The subpoena to Mr. Gertz follows an investigation of the leak ordered by Judge Carney in response to a motion by Chi Mak’s wife, Rebecca Chiu, who was also a defendant in the case. The leak probe, carried out by the FBI and prosecutors in Washington, was first reported by The New York Sun.

“The government conducted a comprehensive, year-long investigation and interviewed over 500 persons of interest,” Judge Carney wrote in an order dated May 1. He said government lawyers admitted there was a violation of the rule requiring grand jury secrecy, but were “unable to determine the identity of the person or persons who leaked the grand jury information to Mr. Gertz.”

Judge Carney’s order noted that Mr. Gertz attributed to “senior Justice Department officials” the details about a new indictment in the case. However, the judge did not indicate whether he had weighed the impact forcing Mr. Gertz to testify might have on his work or on the public’s ability to learn about government activities.

“The Court finds it necessary to subpoena Mr. Gertz to testify regarding the identity of the source that provided him with the grand jury information,” Judge Carney wrote.

The subpoena for Mr. Gertz is just the latest in a series of high-profile efforts in the federal courts to compel journalists to identify sources who were granted confidentiality. In one widely publicized case in 2005, a reporter for the New York Times, Judith Miller, spent 85 days in jail after refusing to identify her reporting sources to a special prosecutor and a grand jury investigating the leak of a CIA operative’s identity.

In March of this year, a federal judge in Washington, Reggie Walton, ordered a former reporter for USA Today, Toni Locy, to pay a fine quickly escalating from $500 to $5000 a day for failing to name her sources for stories about an inquiry into the 2001 anthrax attacks. The financial penalties, which Ms. Locy was ordered to pay from her own pocket, came in a civil suit brought by a person investigated in the attacks, Steven Hatfill. A federal appeals court has stayed Judge Walton’s order while the former journalist appeals.

In addition, a New York Times reporter who covers the CIA, James Risen, is fighting a federal grand jury subpoena for sources of information about an attempt to penetrate Iran’s nuclear program. The effort was discussed in one of Mr. Risen¹s books. The status of his subpoena is unclear because records in the dispute have been filed under seal before a judge in Alexandria, Va.

“If Gertz is ordered to testify, he resists, and is held in contempt, then it’s a repeat of the same scenario we’ve been dealing with,” Ms. Kirtley said.

The professor noted that the 9th Circuit Court of Appeals, which handles cases out of California and is considered the most liberal appeals court, has not been particularly friendly to journalists under subpoena. In 2006, it turned down an appeal from a freelance videographer, Joshua Wolf, who was fighting a grand jury subpoena for videotape of a protest in which a police car was damaged. Mr. Wolf spent 226 days in jail before he was released after posting his video online.

Some journalists and lawyers for the press are urging passage of a shield law that would make it more difficult to subpoena journalists in some federal cases. Most states have such protections.

Mr. Gertz, who has built his reputation on obtaining and disclosing highly classified documents, escaped an earlier attempt to wrangle him into the Mak case. In 2006, a defense lawyer for Chi Mak tried to subpoena Mr. Gertz to testify about how the surveillance in the case originated. A book the reporter published that year, “Enemies: How America’s Foes Steal Our Vital Secrets and How We Let It Happen,” said the spy probe was triggered by a mole with knowledge of Chinese intelligence gathering in America. However, Judge Carney quashed the earlier subpoena, ruling that any information the journalist had was not relevant to the legality of the warrants which authorized wiretaps, bugs and covert searches.

At a trial last year, Chi Mak was convicted of being an unregistered agent for China. His wife, his brother, and two other relatives subsequently pled guilty. Earlier this year, Judge Carney sentenced Chi Mak to over 24 years in prison.