"The time for needless delay of this legislation has passed," the Vermont Democrat said in prepared remarks. "We simply have no idea how many newsworthy stories have gone unwritten and unreported out of fear that a reporter would be forced to reveal a source, or face jail time."

Even if the Judiciary Committee gets through a growing list of amendments and approves the bill, it faces significant opposition in the full Senate and the White House.

The Bush administration opposes the measure on grounds it would make it harder to trace the source of leaks that could harm national security.

So does U.S. Attorney Patrick Fitzgerald, who subpoenaed reporters to testify against White House aide I. Lewis "Scooter" Libby in a case that grew out of Fitzgerald's CIA leak probe. Libby was convicted of obstruction, perjury and lying to the FBI; his sentence was commuted by President Bush.

"The proposed shield law poses real hazards to national security and law enforcement," Fitzgerald writes in an opinion piece Thursday in The Washington Post.

A shield law got a boost Thursday from House Speaker Nancy Pelosi, D-Calif., who supports it but has not yet scheduled a floor vote. If the measure makes it out of the Senate, it likely would have to be reconciled with the version passed earlier this year in the House Judiciary Committee.

"I have long supported a federal media shield law, without which freedom of the press is threatened," Pelosi said in prepared remarks to the Associated Press Managing Editors. "The government's policies and actions should protect and preserve your ability to speak truth to power. And I know we can do this with appropriate national security safeguards."

Leaks of classified information harm national security, Fitzgerald said, and a federal shield law "would have the unintended but profound effect of handcuffing investigations of such leaks."

In a companion piece in the Post, former Bush administration solicitor general Theodore B. Olson argued for the proposed federal law, saying state shield laws have worked well.

"Reporters do not expect to be above the law," writes Olson, who represented some reporters in the CIA leak case. "But they should receive some protection so they can perform their public service in ensuring the free flow of information and exposing improper conduct without risking jail sentences."

The measure creating the first federal shield law for reporters is a bipartisan compromise. The panel could not finish considering all amendments a week earlier.

In an objection echoed by some Republican senators, the Justice Department and Bush's intelligence officials say that leaked reports of intelligence activities have been a valuable source of information to the nation's adversaries. Sen. Jon Kyl, R-Ariz., touted Justice Department statistics that show that 19 subpoenas have been issued for reporters' source-related material since 1992, and only four have been approved since 2001.

But supporters point out that the bill includes exemptions for cases in which investigators are tracking acts of terrorism in the U.S. and other countries. An amendment by Sen. Sam Brownback, R-Kan., would keep accused spies, agents of foreign countries and terrorists from claiming the same protections extended to journalists.

The bill is supported by 50 news organizations, including The Associated Press.

The House Judiciary Committee passed its own bill in August.

The bill number is S. 2035.