Rice suggested that President Barack Obama had jeopardized America’s position as the most successful political and economic experiment in history," the Associated Press reported.
The former official in both Bush administrations addressed issues of free trade, foreign aid, immigration policy, education and national defense in her speech Wednesday night, a prepared version of which was printed in full by The Washington Post.
She said there that the US must continue to lead the way in supporting free people and free markets, or otherwise risk chaos.
The US has since the end of World War II had an answer — we stand for free peoples and free markets, we are willing to support and defend them — we will sustain a balance of power that favors freedom.
The US still had a role in promoting democracy in such places as China, Uganda, Zimbabwe and Southeast Asia, despite "a sense that we have carried these burdens long enough."
Mitt Romney and Paul Ryan understand this reality — that our leadership abroad and our well being at home are inextricably linked. They know what needs to be done.
Earlier on Wednesday, Rice said that she would not serve in a Romney administration, telling CBS’s "This Morning": "I am a very happy professor at Stanford."
Rice is a professor of political science at Stanford University in California, where she also served earlier as provost in charge of academic affairs and the university budget.
"That's a no," she said when pressed on the issue.
In an interview with CNN's Piers Morgan, the first African-American woman to serve as Secretary of State also stressed that she felt Romney was "speaking to black voters."
She said that while she shared deep "pride" in seeing the first African American elected president, Obama’s policies did not serve the broader country's best interests.
"One ultimately has to ask, are these policies helping America, and in particular, are they helping some of the most vulnerable among minorities?" she asked.
"Kids in failing schools, unemployed youth. And the policies aren’t helping those constituencies."
Rice, 57, grew up in Alabama during a period of racial segregation throughout much of the US South.