A program President George W. Bush ordered allowing warrantless spying on Americans with suspected terrorist ties also captured purely domestic communications, sources within the program admit.

Privately, officials admit the calls were snagged despite claims from the White House that one end of the intercepted conversations took place on foreign soil.

The officials claim the National Security Agency’s interception of communications between people within the United States was apparently accidental, caused by technical glitches in determining whether a communication was in fact “international.”

There was no immediate comment from the White House.

Bush and senior administration officials have argued that the policy of authorizing — without court orders — eavesdropping on international phone calls and e-mails by Americans suspected of links to terrorism was legal and necessary to help defend the country after the September 11 attacks.

The White House has sought to play down the impact on civil liberties, arguing the program was narrow in scope and that key congressional leaders were briefed about it.

A 1978 law, the Foreign Intelligence Surveillance Act, makes it illegal to spy on U.S. citizens in the United States without court approval.

Officials, who spoke on condition of anonymity, would not discuss the number of accidental intercepts.

National security and telecommunications experts said that even if the NSA stuck closely to the rules set by the White House, the logistics of the program may make it difficult to ensure that the rules are being followed, the newspaper reported.

With roaming cell phones, internationally routed e-mail and voice-over Internet technology, “it’s often tough to find out where a call started and ended,” Robert Morris, a former NSA official, said. “The NSA is good at it but it’s difficult even for them. Where a call actually came from is often a mystery.”