Ukraine crisis: US blames Russia for violence
28 August 2014 Last updated at 22:38 BST
US President Barack Obama and Nato have accused Russia of stoking violence in eastern Ukraine.
Russia denies claims by Nato that more than 1,000 Russian troops are now operating in the region.
Meanwhile pro-Russian rebels have opened a new front in the south of Ukraine, seizing the coastal town of Novoazovsk.
Diplomatic correspondent James Robbins reports.