The Bush administration has appealed a federal judge's ruling that the government's controversial domestic surveillance program is unconstitutional.

Lawyers for the U.S. Justice Department filed the documents Friday in a federal appeals court in the midwestern U.S. state of Ohio.

President Bush authorized the program shortly after the September 11, 2001 terrorist attacks in the United States.

The program monitors without a court's permission international phone calls and e-mail to and from the U.S. The surveillance involves people who the government suspects may have links to terrorism.

The American Civil Liberties Union filed the lawsuit against the domestic spying program on behalf of many lawyers and scholars who say it hurts their work with contacts abroad.

A federal judge in the northern U.S. state of Michigan ruled in August that the program violates Americans' free speech and privacy rights. A higher court over-ruled that decision, and said the administration could continue the program while it appeals the earlier decision.

President Bush says the program is vital in the fight against terrorism.