He repeated on Saturday that only a small number of US soldiers deployed in Iraq took part in abusing inmates at the Abu Ghuraib prison, as pressure mounted on Washington about the scandal.
"In recent days, America and the world have learned of shocking conduct in Iraqi prisons by a small number of American servicemen and women," Bush said.
"These individuals had been given the responsibility of overseeing Iraqis in American custody, and doing so in a decent and humane manner, consistent with US law and the Geneva Conventions," he continued.
"Instead, we have seen shameful images of prisoners being subjected to abuse and humiliation."
Still, Bush stressed: "What took place in that Iraqi prison was the wrongdoing of a few, and does not reflect the character of the more than 200,000 military personnel who have served in Iraq since the beginning of Operation Iraqi Freedom."
Bush defends military
He said members of the US military continued to represent "the best of America".
"The world has been shocked and angered, and America's moral leadership's been undercut by the terrible pictures of a small number of our US
military people abusing Iraqi prisoners"
retired US general
US Defence Secretary Donald Rumsfeld told Congress on Friday there were additional photos from Abu Ghuraib prison that were even more "blatantly sadistic" than those already made public. He offered his "deepest" apologies to the prisoners and their families during the hearings.
The Pentagon is conducting several formal investigations led by senior military officials.
CBS television ignited the abuse controversy on 28 April, when it aired photographs of naked Iraqi prisoners shown in sexually humiliating poses, sometimes with grinning male and female soldiers looking on or pointing.
The scandal has damaged the United States' reputation abroad and seriously hurt its credibility in the Arab world at a time of surging unrest in Iraq.
Many Democrats are calling for
Donald Rumsfeld's resignation
The president said the US had sent troops into Iraq to liberate the country, return sovereignty to the Iraqi people and make America and the world more secure.
Citing the rising US toll in Iraq, he conceded the military had gone through "a difficult few weeks".
He reaffirmed the US commitment to hand over authority to Iraqis on 30 June, saying that on that date, an independent Iraqi interim government would take over the functions of the state, from basic services to law enforcement to diplomacy, and the Coalition Provisional Authority would cease to exist.
But Bush made clear the US role in Iraq would continue beyond the handover date.
"We have no intention of leaving that nation at the mercy of thugs and murderers," he insisted. "We're determined to help build a free and stable Iraq, a nation at peace with its neighbours and with the world."
Still, Democrats said Bush had not yet done enough.
"The world has been shocked and angered, and America's moral leadership's been undercut by the terrible pictures of a small number of our US military people abusing Iraqi prisoners," retired general Wesley Clark said in the Democrats' radio response.
"The president apologised; he's recognised and stated that these acts were 'stains on our honour'. And it's right that he's done so.
"But apologies are not enough. These criminal acts of abuse must be investigated fully and those responsible must be held accountable under law. We must fix our training and procedures so this cannot happen again.
"Amends must be made to Iraqis who suffered these humiliations through real and symbolic gestures, such as the dismantling of Abu Ghuraib prison itself. This is a mission in trouble," Clark declared.