The threats, pressure and ultimatums have come and gone, but Russian President Vladimir Putin has maintained Moscow's uncompromising demands in the war in Ukraine, raising fears he could use a planned summit with US President Donald Trump in Alaska to coerce Kyiv into accepting an unfavourable deal.

President Xi Jinping told his Russian counterpart, Vladimir Putin, in a phone call on Friday that China was pleased to see Moscow and Washington improving their relations, state media said.