The sentence handed down last month was significantly shorter than the 35 years prosecutors had recommended, but could have been shorter still had Ressam agreed to testify against two of his alleged co-conspirators.

In a statement announcing his decision to appeal, U.S. Attorney John McKay said the standard sentencing range for the crimes Ressam committed is 65 years to life.

"Ahmed Ressam plotted to kill hundreds of innocent Americans," McKay said. "His powerful explosives put lives at risk on the ferry Coho and in Port Angeles. We believe his actions warrant a sentence above 22 years, and that the district judge erred in imposing the sentence."

In an interview with The Associated Press, McKay said another issue in the appeal could be comments U.S. District Judge John C. Coughenour made during the sentencing. Coughenour lambasted Bush administration policies for handling "enemy combatants" in the war on terror, and said Ressam's trial and sentencing had proved that the U.S. court system is perfectly capable of prosecuting terror suspects.

"We did not need to use a secret military tribunal, detain the defendant indefinitely as an enemy combatant or deny the defendant the right to counsel," Coughenour said at the time. "The message to the world from today's sentencing is that our courts have not abandoned our commitment to the ideals that set our nation apart."

Asked whether the judge's comments were appropriate, McKay said, "I'm going to let the 9th Circuit decide that."

"This appeal goes more to the length of the sentence than to any comments Judge Coughenour made at the sentencing," McKay said. "We haven't written the briefs yet, we're leaving all of our options for the appeal open, and that may well be one of them. I have a huge amount of respect for Judge Coughenour."

Ressam's lawyers, Thomas Hillier and Michale Filipovic, were unavailable for comment Friday, the U.S. Public Defender's Office said.

With credit for time served and three years off for good behavior, Ressam, 38, could be out of prison in 14 years. He likely would then be deported or sent to France, where he has been convicted in absentia of terror-related crimes.

Ressam was arrested Dec. 14, 1999, as he tried to enter the United States at Port Angeles with explosive materials in the trunk of his rental car.

After being convicted of terrorist conspiracy and explosives charges at his 2001 trial, Ressam began cooperating in hopes of winning a reduced sentence. He told investigators about the operation of terrorist camps and disclosed the identities of potential terrorists, the use of safe houses and other details.