"In a world where evil is still very real, democratic principles must also be backed with power in all its forms: Political and economic, cultural and moral, and yes, sometimes military," Rice said on Friday, in a speech at Princeton University in the northeastern state of New Jersey.
Alluding to countries such as Germany and France that opposed the US-led invasion of Iraq, Rice said: "Any champion of democracy who promotes principles without power can make no real difference in the lives of oppressed people."
Appointed as the top US diplomat by President George Bush after his 2004 re-election, Rice sought to justify US military action as part of an effort to promote democracy in the Middle East and defuse terror threats.
Oppression and despair
"If you believe, as I do and as President Bush does, that the root cause of September 11 was the violent expression of a global extremist ideology, an ideology rooted in the oppression and despair of the modern Middle East, then we must seek to remove the very source of this terror by transforming that total region," she said.
While popular support for the US presence in Iraq is deteriorating and some experts are warning that Iraq could descend into civil war, Rice said that the Bush administration's approach would create more stability in the long term.
"We must recognise, as we do in every other region of the world, that liberty and democracy are the only guarantees of true stability and lasting security"
US secretary of state
"Some would argue that this broad approach to the problem is making the world less stable by rocking the boat and wrecking the status quo. But this presumes the existence of a stable status quo that does not threaten global security. This is not the case.
Liberty and democracy
"We must recognise, as we do in every other region of the world, that liberty and democracy are the only guarantees of true stability and lasting security," she said.
Ousted Iraqi president Saddam Hussein, whom Rice described as "a monster", simply "could not be a part of anyone's vision for a better Middle East".
The path to a peaceful Iraq, however, "is made more difficult by the brutal insurgency".
"This is not some grassroots coalition of national resistance.
"These are merciless killers who want to provoke nothing less than a full-scale civil war among Muslims across the entire Middle East. And having done so, they would build an empire of terror and oppression," she said.
Rice believes US troops must
stay in Iraq for future security
She also said that withdrawing soon from Iraq was not an option.
"If we quit now ... we will make America more vulnerable. If we abandon future generations in the Middle East to despair and terror, we also condemn future generations in the United States to insecurity and fear."
Force equals failure
A professor of Georgetown University in Doha told Aljazeera that the United States's policy of force has been a failure.
"First, since the beginning of the Iraq war, there was US domestic opposition to the war as well as world opposition in the UN when Kofi Annan said the war was illegitimate, according to international law," Ibrahim Uwais said.
''Secondly, the use of force has led to instability in Iraq. This is why we should inquire what democracy Secretary Rice is speaking about when we are witnessing the big tragedy being inflicted on Iraq."
Uwais said the use of force was dangerous, adding: "To every action there is a reaction, and every military offensive breeds resistance. This path is full of human tragedies.
"Such tragedy might lead to civil war or to creating three volatile mini-states and instability in the whole Gulf region."