As tension runs high in Ukraine, Joe Biden and Vladimir Putin have spoken yet again.
The latest diplomatic attempt between the United States and Russia to resolve tensions over Ukraine achieved nothing.
Presidents Vladimir Putin and Joe Biden exchanged warnings and concerns over the phone but little else, while military activity continues on both sides.
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Moscow has been massing troops in Russia and Belarus near its borders with Ukraine. The buildup is raising fears an invasion is imminent.
Why is the crisis over Ukraine proving so hard to resolve?
Pavel Felgenhauer – defence analyst and columnist at Novaya Gazeta
Matthew Bryza – senior fellow at the Atlantic Council; former US diplomat
Glenn Diesen – professor of international relations at the University of South-Eastern Norway; editor Russia in Global Affairs