Asked in a US television interview whether the camp should be shut down, Mr Bush said: “We’re exploring all alternatives as to how best to do the main objective, which is to protect America. What we don’t want to do is let somebody out that comes back and harms us”.
The United States has faced international criticism of the detention centre at the naval base since it was opened in early 2002 to house alleged Taliban and al-Qaida militants.
There are currently around 540 inmates from 40 countries detained there.
Controversy has risen in recent weeks over allegations about the abuse of Muslim holy books at Guantanamo, and former president Jimmy Carter this week joined US politicians who have called for the camp’s closure.
But Defence Secretary Donald Rumsfeld said the United States was not considering closing Guantanamo.
Mr Bush and Mr Rumsfeld both insist prisoners at the camp have been treated humanely.
The US president told Fox News television: “I first of all want to assure the American people that these prisoners are being treated in accordance with the Geneva Convention.”
“I say in accordance with, because these weren’t normal military-type fighters. They had no uniforms. They had no government structure. These were terrorists, swept up off the battlefield.
“And it’s in our nation’s interest that we learn a lot about those people that are still in detention, because we’re still trying to find out how to better protect our country.”
Mr Bush insisted all allegations of abuse were investigated.
He also reaffirmed his comment that an Amnesty International report likening Guantanamo to a “gulag” was “absurd”.