"It's the kind of capability if we'd had before 9/11 might have led us to be able to prevent 9/11," Cheney said in an interview with ABC America’s "Nightline" program.
President George W Bush admitted on Saturday that he had authorised secret wiretaps by the National Security Agency on US and foreign citizens in the US just after the 2001 attacks on New York and Washington, without the need for approval from a special court.
In his weekly radio address, Mr Bush confirmed a New York Times report that he had authorised eavesdropping on overseas communications by people living in the US who were suspected of terrorist activities.
Outcry
The admission has drawn outcry from human rights groups while some lawmakers have accused the president of breaking the law because normally a court warrant is needed for such action under the Foreign Intelligence Surveillance Act.
But Mr Cheney reminded that two of the September 11 terrorists were in San Diego, California before the attacks and communicating with Al-Qaeda sources outside the US.
"We didn't know it," he said. "The 9/11 Commission talks about it. If we'd had this capability, then we might well have been able to stop it."
He said that the communications that are being monitored involved only known terrorist suspects.
"And in fact, it is consistent with the president's constitutional authority as commander in chief," he insisted. "It's consistent with the resolution that was passed by the Congress after 9/11."