As she travelled from Berlin to Bucharest, then Kiev and finally
Brussels, Ms Rice responded to allegations that the Central Intelligence Agency had flown "prisoners" in the US war on terror through European airspace.
In Ukraine, she insisted Washington's obligations under an international convention prohibiting cruel, inhuman or degrading treatment "extend to US personnel wherever they are, whether they are in the US or outside the US".
A day later, she raised the contentious prisons issue first at an informal dinner at the headquarters of NATO in Brussels, attended by 32 foreign ministers from the military alliance and the European Union.
EU ministers satisfied
Several European ministers declared afterwards they were "satisfied" with her explanations on the CIA's use of airports in a process known as "rendition", forcibly sending prisoners to places where they can be charged.
NATO secretary general Jaap de Hoop Scheffer said Ms Rice's remarks had "cleared the air".
But the top US diplomat failed to clarify whether the CIA had secret prisons in Europe where suspected terrorists were being held, and often chose instead to hide behind security secrecy laws.
Nevertheless she had the support of Europe's diplomats.
"I appreciate the supportive comments that a number of colleagues have made," she said in Brussels. "I appreciate the fact that people recognise the dilemmas we face."
But asked if she thought that European public opinion remained to be convinced about US policy, she conceded that more efforts might be needed.
"I think that it's only natural that sometimes we have these discussions. Questions, concerns arise, we should discuss them in a serious way among friends," she told reporters.
"Whether or not it will continue to be a matter of discussion I can't say. I'm perfectly happy to continue to have this discussion." US officials said they would indeed continue.
Ms Rice has found herself on the front line over the secret prisons at a delicate time in transatlantic relations, after both sides have made considerable efforts to move on from the tensions raised by the war in Iraq.
In the name of the European Union, British Foreign Secretary Jack Straw, whose country holds the bloc's rotating presidency and is Washington's main ally in Iraq, said he would seek clarification from Ms Rice over the prisons.
Torture denial
But with her credibility on the line over her country's treatment of terror suspects lost in the system without trial or means of appeal, Ms Rice took shelter behind US President George W Bush.
"The United States is quite clear and quite determined to carry out the president's policy. The US does not engage in torture, doesn't condone it, doesn't expect its employees to engage in it."
But she said abuses like those committed by US personnel at the notorious Abu Ghraib prison in Iraq could not be ruled out, although she noted those responsible would be punished.
"Will there be abuses of policy? That is entirely possible. Because just because you're a democracy it doesn't mean you're perfect," she said.
"That is the only promise that we can make to people: if we find abuses we will investigate them fully and punish them."
Ms Rice's message had clearly evolved from the one she delivered on leaving Washington on Monday.
"It is up to those governments and their citizens to decide if they wish to work with us to prevent terrorist attacks against their own country or other countries, and decide how much sensitive information they can make public," she said then.