He reiterated that the US does not view its relationship with Russia as a "sort of continuation of the Cold War", adding "this is not Rocky IV". The 1990 film depicted a battle between East and West, in which Rocky Balboa fights then-Soviet Union boxer Ivan Drago.
Nato defence ministers warned they considered Ukraine's future to be "key to Euro-Atlantic security" and assured the new Government in Kiev that the alliance would back its "sovereignty, independence [and] territorial integrity".
"A sovereign, independent and stable Ukraine, firmly committed to democracy and the rule of law, is key to Euro-Atlantic security," their statement said.
The comments appear to be a direct response to comments by high-ranking Russian officials, including Dmitry Medevedev, the Prime Minister, who said this week that the revolution in Ukraine posed "a real threat to our interests".
While many throughout Ukraine see the revolution as an uprising against a corrupt and discredited elite, Russian-speaking Ukrainians and ethnic Russians are alarmed by what they see as nationalist and Russophobic elements among the groups that have seized control in Kiev.
Russia has warned it may act to protect its citizens in the Russian-majority region of Crimea, where it maintains a naval base and a 25,000-strong garrison.
The new Government in Kiev continued to consolidate its grip on power yesterday, with the Acting President, Oleksandr Turchynov, assuming command of the armed forces. Arseniy Yatsenyuk, a former Foreign Minister, was proposed as the country's new Prime Minister. A list of suggested Cabinet members was read out to the crowd in Independence Square. It will go before Parliament for confirmation today.
Parliament has disbanded the Berkut, a special riot police unit blamed for much of the previous violence against protesters. That move heightened fears in Russian-speaking parts of Ukraine. The anti-revolutionary Mayor of Sevastopol has promised to retain the unit as part of his municipal police force. At least one person died and seven were injured in a stampede after rival demonstrators clashed in Simferopol.
Radical policing at rubbery checkpoint
The task of controlling entry to a city of almost three million has fallen to a 30-year-old electrician called Andreiy, who mans a motorway checkpoint made of old tyres.
Along with four other revolutionaries clad in motley camouflage, he stands guard on the northeastern fringe of Kiev.
In the aftermath of the revolution, Ukraine's police have disappeared from the streets and handed their duties over to revolutionaries. In other capitals, the sudden withdrawal of the police would risk a general collapse of law and order. But Kiev is different: shops and offices have reopened and traffic fills the streets. Even banks and jewellers feel confident enough to open their doors.
Andreiy and his comrades keep watch for buses packed with "tituskhi" - the young criminals hired by the old regime to harass protesters. "If we see a suspicious vehicle, we take the registration number and contact the revolutionaries in the centre of Kiev and ask them to stop it. If they call us and tell us to stop a car, then we do."
The revolutionaries have shown their ability to enforce order. The central area which they have controlled for months is packed with expensive shops, including branches of Gucci and Louis Vuitton. These businesses have closed their doors, but their windows are unbroken and there is no visible sign of looting.
