James Risen

While the Bush administration had defended its program of wiretapping without warrants as a vital tool that saved lives, a new government review released Friday said the program's effectiveness in fighting terrorism was unclear.

The National Security Agency is facing renewed scrutiny over the extent of its domestic surveillance program, with critics in Congress saying its recent intercepts of the private telephone calls and e-mail messages of Americans are broader than previously acknowledged.

The National Security Agency has been campaigning to lead the government's rapidly growing cybersecurity programs, raising privacy and civil liberties concerns among some officials who fear that the move could give the spy agency too much control over government computer networks.

The National Security Agency intercepted private e-mail messages and phone calls of Americans in recent months on a scale that went beyond the broad legal limits established by Congress last year.

In a rare public ruling, a secret federal appeals court has said telecommunications companies must cooperate with the government to intercept international phone calls and e-mail of American citizens suspected of being spies or terrorists.

A Congressional oversight panel plans to ask the National Security Agency to start an investigation into new evidence that the agency illegally wiretapped a Muslim scholar in Northern Virginia and concealed the eavesdropping during a 2005 trial in which the scholar was convicted on terrorism charges.