Officials refused to identify the six suspects being held in US custody and suggested their identities might be kept secret during any military trial.

That drew criticism from the chairman of the American Bar Association's task force on the treatment of detainees in the war on terrorism.

"The State Department issues a report every year in which it criticizes those nations that conduct trials before secret military tribunals. What I'm hearing sounds alarmingly like something similar," said Neal Sonnett, also a former president of the National Association of Criminal Defense Lawyers.

"If they're going to be charged by military tribunals then they have a right to full due process and the public has a right to know who's being tried and what the charges are and the government has an obligation to run these tribunals in a fair and transparent way."

All six suspects are believed to be either members of the al-Qaeda terrorist network or otherwise involved in terrorism, said two Pentagon officials who briefed reporters on condition of anonymity Thursday.

Australian detainee David Hicks, who is being held at the US Navy base at Guantanamo Bay, Cuba, likely will be one of the six, said his lawyer, Stephen Kenny.

Hicks, a Muslim who fought with the Kosovo Liberation Army, called his parents 17 days after the Sept. 11 attacks to say he was with the Taliban. He also allegedly threatened to kill an American upon his arrival at Guantanamo, US officials said.

Some of the six may have attended terrorist training camps and some were involved in raising money and recruiting for terrorist groups, the officials said. Under Bush's order creating the military tribunals, only people who are not US citizens may be subject to such trials.

Unlike traditional criminal trials, the proceedings of military tribunals can be kept much more secret. The United States has not convened such a tribunal since World War II.