WASHINGTON (AP) — Self-proclaimed Sept. 11 mastermind Khalid Sheikh Mohammed and four other Guantanamo Bay detainees will be sent to New York to face trial in a civilian federal court, while five other suspects will be sent to military commissions, an Obama administration official said Friday.

The official said Attorney General Eric Holder plans to announce the decision later in the morning. The official is not authorized to discuss the decision before the announcement, so spoke on condition of anonymity.

Without confirming details of the decision, President Barack Obama said it was a legal and national security matter. “I am absolutely convinced that Khalid Sheikh Mohammed will be subjected to the most exacting demands of justice,” Obama said at a joint news conference in Tokyo with Japanese Prime Minister Yukio Hatoyama.

Bringing such notorious suspects to U.S. soil to face trial is a key step in Obama’s plan to close the terror suspect detention center at Guantanamo Bay, Cuba. Obama initially planned to close the detention center by Jan. 22, but the administration is no longer expected to meet that deadline.

It is also a major legal and political test of Obama’s overall approach to terrorism. If the case suffers legal setbacks, the administration will face second-guessing from those who never wanted it in a civilian courtroom. And if lawmakers get upset about notorious terrorists being brought to their home regions, they may fight back against other parts of Obama’s agenda.

The New York case may also force the court system to confront a host of difficult legal issues surrounding counter-terrorism programs begun after the 2001 attacks, including the harsh interrogation techniques once used on some of the suspects while in CIA custody. The most severe method — waterboarding, or simulated drowning — was used on Mohammed 183 times in 2003, before the practice was banned.

Holder will also announce that five other detainees, including a major suspect in the bombing of the USS Cole, Abd al-Rahim al-Nashiri, will face justice before a military commission, the official said.

It was not immediately clear where commission-bound detainees like al-Nashiri might be sent, but a military brig in South Carolina has been high on the list of sites under consideration.

The actual transfer of the detainees from Guantanamo to New York isn’t expected to happen for many more weeks because formal charges have not been filed against most of them.

The attorney general has decided the case of the five Sept. 11 suspects should be handled by prosecutors working in the Southern District of New York, which has held a number of major terrorism trials in recent decades at a courthouse in lower Manhattan, just blocks from where the World Trade Center towers tumbled on Sept. 11, 2001.

Holder had been considering other possible trial locations, including Virginia, Washington, D.C., and a different courthouse in New York City. Those districts could end up conducting trials of other Guantanamo detainees sent to federal court later on.

The attorney general’s decision in these cases comes just before a Monday deadline for the government to decide how to proceed against 10 detainees facing military commissions.

In the military system, the five Sept. 11 suspects had faced the death penalty, but the official would not say if the Justice Department would also seek capital punishment against the men once they are in the federal system.

The administration has already sent one Guantanamo detainee, Ahmed Ghailani, to New York to face trial, but chose not to seek death in that case.

At the last major trial of al-Qaida suspects held at that courthouse in 2001, prosecutors did seek death for some of the defendants.

Mohammed already has an outstanding terror indictment against him in New York, for an unsuccessful plot called “Bojinka” to simultaneously take down multiple airliners over the Pacific Ocean in the 1990s.

Some members of Congress have fought any effort to bring Guantanamo Bay detainees to trial in the United States, saying it would be too dangerous for nearby civilians. The Obama administration has defended the planned trials, saying many terrorists have been safely tried, convicted, and imprisoned in the United States, including the 1993 World Trade Center bomber, Ramzi Yousef.

Mohammed and the four others — Waleed bin Attash, Ramzi Binalshibh, Mustafa Ahmad al-Hawsawi and Ali Abd al-Aziz Ali — are accused of orchestrating the attacks that killed 2,973 people on Sept. 11, 2001.

Mohammed admitted to interrogators that he was the mastermind of the attacks — he allegedly proposed the concept to Osama bin Laden as early as 1996, obtained funding for the attacks from bin Laden, oversaw the operation and trained the hijackers in Afghanistan and Pakistan.

The charges against the others are:

— Bin Attash, a Yemeni, allegedly ran an al-Qaida training camp in Logar, Afghanistan, where two of the 19 hijackers were trained. Bin Attash is believed to have been bin Laden’s bodyguard. Authorities say bin Laden selected him as a hijacker, but he was prevented from participating when he was briefly detained in Yemen in early 2001.

— Binalshibh, a Yemeni, allegedly helped find flight schools for the hijackers, helped them enter the United States and assisted with financing the operation. He allegedly was selected to be a hijacker and made a “martyr video” in preparation for the operation, but was unable to get a U.S. visa. He also is believed to be a lead operative for a foiled plot to crash aircraft into London’s Heathrow Airport.

— Ali allegedly helped nine of the hijackers travel to the United States and sent them $120,000 for expenses and flight training. He is believed to have served as a key lieutenant to Mohammed in Pakistan. He was born in Pakistan and raised in Kuwait.

— Mustafa Ahmad al-Hawsawi, a Saudi, allegedly helped the hijackers with money, western clothing, traveler’s checks and credit cards. Al-Hawsawi testified in the trial of Zacarias Moussaoui, saying he had seen Moussaoui at an al-Qaida guesthouse in Kandahar, Afghanistan, in early 2001, but was never introduced to him or conducted operations with him.

The official said the four others headed to military commissions are:

— Omar Khadr, a Canadian who was 15 when captured after allegedly killing an American soldier during a 2002 battle in Afghanistan.

— Ahmed Mohammed al Darbi, who allegedly met with Osama bin Laden, trained at an al-Qaida terrorist camp, and plotted to blow up a ship in the Strait of Hormuz or off Yemen.

— Ibrahim Ahmed Mahmoud al Qosi, accused of acting as al-Qaida’s accountant, paymaster and supply chief during the 1990s when the terror network was centered in Sudan and Afghanistan.

— Noor Uthman Muhammed, charged with being a weapons instructor and deputy commander at an al-Qaida training camp.