"Obviously, we're in a very difficult spot right now, and we hope that we can find the steps forward that provide for the end of this war in a negotiated way and the prevention of any war in the future," Rubio said at a NATO meeting in Antalya.

"So a lot of work. We remain committed to that. Obviously, like everyone else, impatient, we want to see it happen, but it's difficult. But you know, hopefully progress will be made here soon," he added.

The comments come ahead of potential direct talks between Ukraine and Russia to end the war, with US President Donald Trump pressing both sides for results.

"He's open to virtually any mechanism that gets us to a just, enduring and lasting peace, and that's what he wants to see," Rubio said.

NATO chief Mark Rutte meanwhile said that he was "cautiously optimistic" for progress towards peace in Ukraine, but that it was up to Russia to take the "next steps necessary".

"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.

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

Russian President Vladimir Putin appears poised to skip talks in Istanbul that he initially proposed, and which Ukraine's leader Volodymyr Zelensky agreed to attend in person.

Instead Moscow has dispatched a team headed by hardline former culture minister Vladimir Medinsky to 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.

Despite the hopeful tone from the NATO boss, European foreign ministers were downbeat on Russia's willingness to make advances.

"The best we can hope for in these technical discussions is indeed a ceasefire, an immediate, unconditional ceasefire, that would allow for proper peace negotiation," France's Jean-Noel Barrot said.

He insisted talks needed to avoid the same "traps" that caused negotiations to fail back in 2022 and warned that Europe was preparing "massive" sanctions on Russia financial and energy sectors if the Kremlin doesn't make concessions.