Obama: Russia must pull back troops from Ukraine border
28 March 2014 Last updated at 15:57 GMT
US President Barack Obama has urged Russia to "move back its troops" on Ukraine's border and lower tensions.
Russia is believed to have massed a force of several thousand troops close to Ukraine's eastern frontier.
Mr Obama told CBS News "Because you are bigger and stronger taking a piece of the country, that is not how international law and international norms are observed in the 21st Century".