"Direct talks are now underway and this is important progress. But Russian attacks like those last night, do not signal seriousness about peace," Rutte said in an address to Ukraine's parliament.

Russia launched the "most powerful" attack so far this year on Ukraine's battered energy facilities overnight, Kyiv said, leaving hundreds of thousands without heating in glacial temperatures ahead of a fresh round of talks in Abu Dhabi.

Rutte said he was urging NATO countries to "dig deep into their stockpiles" to provide more urgently needed air defences to Ukraine as it struggles to stave off Moscow's bombardments.

The head of the Western military alliance insisted that its "attention has not been diverted" from supporting Kyiv despite a crisis over US demands on Greenland.

Rutte said European members of NATO were willing to provide strong guarantees and deploy forces to Ukraine to make sure any ceasefire was enduring.

"The security guarantees are solid, and this is crucial -- because we know that getting to an agreement to end this terrible war will require difficult choices," he said.

"Ukraine needs to know with absolute certainty -- that whatever sacrifices you've made, the lives you've lost, the devastation you've endured -- will not be at risk of repetition."