"I'm still cautiously optimistic that if also the Russians are willing to play ball, and not only the Ukrainians are doing this... that you could get to some breakthroughs over the next couple of weeks," Rutte said at a NATO meeting in Turkey.

Rutte was speaking ahead of potential peace talks between Ukraine and Russia in Turkey being pushed by US President Donald Trump.

"Ukraine is ready to commit to a ceasefire and immediate negotiations. That's absolutely clear. The ball is now clearly in the Russian court," Rutte said.

"They have to explain what they are doing, why they are here or not, and with what team, or whatever," he added.

Russian President Vladimir Putin has appeared to spurn an offer from Ukraine's leader Volodymyr Zelensky to meet in Istanbul.

Rutte said Russia was sending a "lower level delegation out to Turkey to these peace talks".

"It's now up to the Russians to make sure they take the next steps necessary," he said.