WASHINGTON – The Supreme Court yesterday increased the likelihood of jail time for two reporters, refusing to take up a case that pits the press’s promise to protect confidential sources against a grand jury’s demand for information.

The justices’ decision not to intervene leaves reporters Judith Miller of the New York Times and Matthew Cooper of Time magazine in contempt of court for refusing to reveal their sources in a leak probe involving CIA officer Valerie Plame. Each reporter faces up to 18 months in jail. Officials in the Bush administration leaked Ms. Plame’s identity after her husband, former Ambassador Joseph Wilson, publicly undercut the president’s rationale for invading Iraq.

Special counsel Patrick Fitzgerald, the U.S. attorney in Chicago, said he looks forward to wrapping up the investigation. Time said the magazine would raise additional legal issues to a federal judge on Mr. Cooper’s behalf. Times publisher Arthur Sulzberger Jr. said it was shocking that Ms. Miller faces a prison sentence for doing routine newsgathering on an important public issue and keeping her word to her sources, while not even writing a story.

Ms. Plame’s name was first made public in 2003 by columnist Robert Novak, who cited unidentified senior Bush administration officials for the information. Disclosure of an undercover intelligence officer’s identity can be a federal crime. Mr. Fitzgerald says his only unfinished business is testimony from Mr. Cooper and Ms. Miller.

A federal judge held the reporters in contempt last fall, and an appeals court rejected their argument that the First Amendment shielded them from revealing their sources.

Every state but Wyoming recognizes some level of protection for reporters to keep their sources’ identities confidential.