The makeshift prison camp at the U.S. Naval Base in Guantanamo Bay, Cuba, has almost filled up, prompting the U.S. military to hold off on sending any more Al Qaeda and Taliban fighters there, Pentagon officials told Fox News Wednesday.

Camp X-Ray currently has 150 detainees, which is about all it can handle. A larger facility is in the process of being built.

The prison camp could handle more prisoners if they were to double up in cells, but officials worry that that would make it easier for the detainees to create problems.

Responding to foreign and domestic criticism of the handling of the prisoners, White House spokesman Ari Fleischer was blunt at a press briefing Wednesday.

"These are not mere innocents," Fleischer said. "These are among the worst of the worst, who are being detained because of ... their willingness, their training to go out and kill, destroy and engage in suicide if they can take others with them."

Fleischer said President Bush is concerned that U.S. soldiers at Guantanamo could be harmed in prisoner uprisings. In November, Taliban and Al Qaeda members held near Mazar-e-Sharif, Afghanistan, began a rebellion in which CIA operative Johnny "Mike" Spann, along with numerous Northern Alliance fighters, was killed.

Bush is "perfectly satisfied" that conditions at Guantanamo are humane and fair, Fleischer said. The president also believes that the detainees are linked to Al Qaeda, "and if they were free they would engage in murder once again."

Earlier Wednesday, House Speaker Dennis Hastert, R-Ill., defended the treatment of the suspects as stern but fair.

"Quite frankly, most of these prisoners are Al Qaeda, they're terrorists, they're people who, without conscience, took over 2,000 lives," Hastert said after he and other congressional leaders discussed the issue in a morning meeting with Bush. "I think they need to be dealt with on a very severe basis, yet fair."

Some European allies, human-rights groups, the Red Cross and a United Nations body have criticized U.S. treatment of the detainees, saying they must be given the same rights as prisoners of war under the Geneva Conventions. Hastert disagreed.

"These aren't military people. They don't belong to a country, they don't wear a uniform, they're not part of an army," Hastert said. "It's a unique situation and we'll have to deal with it in a unique way."

Hastert echoed the sentiments of Defense Secretary Donald H. Rumsfeld, who said Tuesday that critics are "misinformed" and America's priority is interrogating the prisoners to get information to prevent attacks, not determining if they qualify as POWs.

"That is pure, simple self-defense of the United States of America," Rumsfeld said.

The controversy centers on the status of the 158 prisoners, mostly suspected Al Qaeda and Taliban fighters, who were flown to Guantanamo after being captured in the Afghanistan war.

Rumsfeld said they eventually would be charged or released. U.S. officials have not decided if they qualify as POWs, and calls them "battlefield detainees." They are being treated "humanely," as the Geneva Conventions require for so-called "unlawful combatants," the defense secretary said.

"No detainee has been harmed. No detainee has been mistreated in any way," Rumsfeld said.

Under the Geneva Conventions, prisoner-of-war status would entitle the detainees to trials under the same procedures as U.S. soldiers — through court-martial or civilian courts — rather than through military tribunals as the Bush administration has proposed.

Al Qaeda fighters probably would not qualify as POWs because they wore no identifying insignia and did not abide by the laws of war, said Jamie Fellner, director of the U.S. program of Human Rights Watch.

But Taliban fighters, whether Afghan or Arab, made up Afghanistan's armed forces and should be entitled to POW status, Fellner said.

Some critics also have raised concerns that some U.S. soldiers, if captured, could be held as "unlawful combatants" by an enemy, because some wore local clothes, not uniforms, when inside Afghanistan. But Rumsfeld said that was unlikely because they carried identification as soldiers.

The Associated Press contributed to this report.