Rice's remarks followed confusion in the United States over whether CIA employees could use means otherwise off limits for U.S. personnel.
It also follows strong and sustained criticism in Europe over techniques such as waterboarding, in which prisoners are strapped to a plank and dunked in water.
"As a matter of U.S. policy," Rice said the United Nations Convention against Torture "extends to U.S. personnel wherever they are, whether they are in the U.S. or outside the U.S."
The U.N. treaty also prohibits treatment that doesn't meet the legal definition of torture, including many practices that human rights organizations say were used routinely at the U.S. military prison camp at Guantanamo Bay, Cuba.
The Bush administration has previously said the ban on cruel, inhumane and degrading treatment did not apply to Americans working overseas. In practice, that meant CIA employees could use methods in overseas prisons that would not be allowed in the United States.
Human rights organizations and critics in Europe have called that a loophole for treatment almost indistinguishable from torture. Prisoners suspected of links to terrorism have been chained to the floors of their cells, denied sleep and led to believe they could be killed.
Rice's five-day European trip has been dominated so far by allegations of secret CIA prisons in Europe and the U.S. treatment of terror suspects in those facilities. Her statements Wednesday reflect ongoing tensions between the White House, Congress and the State and Defense departments over the treatment of detainees.
House and Senate negotiators are expected to include a ban on cruel, inhuman and degrading treatment of foreign terrorism suspects in a final defense bill. The White House has threatened to veto any bill containing such a ban, but President Bush's national security adviser, Stephen Hadley, has been negotiating with its chief sponsor, Sen. John McCain, R-Ariz., to find a compromise.
Separately, Rice delivered a rebuke to Russian President Vladimir Putin over a new law she said infringes on democracy. Drawing a comparison with Ukraine's new democratic government, Rice criticized a Russian law restricting the activities of human rights groups, democracy promoters and other independent organizations.
"Democracy is built, of course, on elections, it's built on principle, it's built on rule of law and freedom of speech," she said.
Rice said U.S. diplomats have told Putin they are concerned about the restrictions.