WASHINGTON — Federal judges would be prohibited from forcing journalists to reveal their confidential sources under legislation headed for a congressional hearing next month. But even as support for the bill grows, lawmakers acknowledged yesterday any such “shield law” probably wouldn't help two reporters now facing jail time for protecting their informants.

A House Judiciary Committee is holding a hearing on the bill May 12, and senators say they are optimistic a Senate Judiciary subcommittee will follow suit.

But Sen. Christopher J. Dodd, D-Conn., said that even if the bill passed quickly, which is unlikely, "the chances are it won't be in time" to keep reporters for Time magazine and The New York Times out of jail.

"Their crime was doing their jobs," said Dodd, adding that, "This is not about conferring special rights and privileges to the media. This is less about protecting journalists than it is about protecting ourselves."

A bipartisan group of House and Senate members said there was growing support for the bill, which would prohibit federal courts from forcing reporters to reveal their confidential sources. The measure would allow federal judges to seek information from reporters as a last resort in extreme situations, but never the name of the source.

Rep. Mike Pence, R-Ind., said the bill "strikes a balance between the public's right to know and the fair administration of justice." A member of the judiciary panel, Pence said lawmakers also had had "very constructive conversations" about the bill with the White House.

First introduced by Dodd, the bill mirrors shield laws in 31 states, and is similar to existing Department of Justice guidelines. The key difference, said Sen. Richard Lugar, R-Ind., is that the bill goes a step further than the Justice rules by offering no exceptions to the source protection.

"That may be the most controversial part," said Lugar, adding that he expected strong opposition to the bill.

The lawmakers said the only way whistleblowers will come forward and reveal government wrongdoing is if they have absolute assurance their identities will be protected.

Journalists have come under increasing pressure from courts to reveal their sources' identities.

Just last week a federal appeals court in Washington refused to reconsider a three-judge panel's ruling compelling Matthew Cooper of Time magazine and Judith Miller of The New York Times to testify before a federal grand jury about their sources or go to jail for up to 18 months.

The two reporters have been called to testify about the leak of an undercover CIA officer's name.

In a separate case, the Associated Press and other news organizations are appealing a federal judge's decision finding five reporters in contempt for refusing to identify their sources for stories about nuclear scientist Wen Ho Lee. Appeals court arguments are set for May 9.

The judge says the information from the reporters is needed so that Lee, who was wrongly suspected of spying, can pursue his privacy lawsuit against government officials.

Last year, TV reporter Jim Taricani of Providence, R.I., was sentenced to home confinement after he refused a court order to reveal the confidential source of an undercover FBI videotape of an alleged bribe. He was released about three weeks ago after serving four months.