WASHINGTON — The 14 so-called high-value detainees who were transferred to Guantanamo Bay, Cuba, from secret CIA prison last year have all been declared enemy combatants and are subject to trial, the Pentagon announced yesterday.

The detainees, including suspected planners of the September 11, 2001, attacks, the USS Cole bombing, and the 1998 bombings of American embassies in Kenya and Tanzania, will now be thrust into a military trial system mired in legal challenges and hampered by lengthy delays.

Deputy Defense Secretary Gordon England has approved the “enemy combatant” designation for all 14, after reviewing recommendations from their Combatant Status Review Tribunals, which took place over the last six months. Pentagon spokesman Bryan Whitman would not say yesterday when Mr. England made the decisions, but he indicated that they were done over a period of time.

Mr. England’s ruling now allows the 14 to be held indefinitely at the detention center and put on trial for war crimes.

But the trial system itself remains under challenge, and it has been called into question by recent court rulings, including a decision by one military judge to throw out a case against a Guantanamo detainee over the wording of the “enemy combatant” designation.

That judge, Army Colonel Peter Brownback, said he had no choice but to throw out the case against terror suspect Omar Khadr because he had been classified as an “enemy combatant” by a military panel years earlier — and not as an “alien unlawful enemy combatant.”

He said the Military Commissions Act, signed by President Bush last year, says only those classified as “unlawful” enemy combatants can face war trials here.