During a media blitz Monday, which included Bush's news conference and a televised appearances by Attorney General Alberto Gonzales, the administration made its case that not only is the president allowed order such actions, members of Congress knew about it.
Gonzales said classified legal reviews have found the program to be within the president's constitutional powers.
Last week The New York Times reported the existence of a National Security Agency program that included domestic spying. The administration insisted Monday the program was limited in scope and only involved people with known terrorist links communicating with people in foreign countries.
Critics argued the NSA could have acted and gotten retroactive judicial approval for the surveillance, but the White House said even that didn't allow for enough flexibility.
Members of Congress say they need to know more about the program. Sen. Arlen Specter, R-Pa., said the issue would likely come up next month during hearings for Samuel Alito's nomination to the U.S. Supreme Court.