Moscow, Russia - Russia said Friday that peace talks with Ukraine were on "pause" as President Donald Trump again warned he was fast running out of patience with his Russian counterpart Vladimir Putin.

Trump's efforts to bring the three-and-a-half-year conflict to an end have faltered in recent weeks, with Russia digging into its hardline demands and refusing to halt its ground and aerial attacks.

The new standoff came as Russia's army staged major military drills with its key ally Belarus on NATO's border, exercises that have spooked the alliance's eastern flank after the downing of Russian drones in Polish airspace this week.

Three rounds of direct peace talks between Russia and Ukraine, as well as a summit between Trump and Putin in Alaska, have failed to make any progress towards ending the fighting.

Russia Putin hails North Korean troops in Ukraine as "heroic" in letter to Kim

Russia Putin hails Trump administration's "sincere" efforts to end Ukraine war ahead of Alaska talks

Moscow's army is grinding forward on the battlefield and Putin has vowed to carry on fighting if his demands for peace – including Ukraine ceding yet more land – are not met.

"Our negotiators have the opportunity to communicate through channels. But for now, it is probably more accurate to talk about a pause" in talks with Kyiv, Kremlin spokesman Dmitry Peskov told reporters in a phone briefing.

"You can't wear rose-tinted glasses and expect that the negotiation process will yield immediate results."

Trump has repeatedly threatened Moscow with additional sanctions if it does not halt its offensive but has failed to follow through, frustrating Kyiv.

"It's sort of running out and running out fast, but it does take two to tango," Trump told Fox News when asked if his patience was being taxed by Russia's refusal to end the conflict.

"It's amazing. When Putin wants to do it, (President Volodymyr) Zelensky didn't. When Zelensky wanted to do it, Putin didn't. Now Zelensky wants to and Putin is a question mark. We're going to have to come down very, very strong," he added.

Russia Russia takes alarming action against Reporters Without Borders

Russia US preparing to increase pressure on Russia after latest brutal assault on Ukraine

Ukraine has ruled out making territorial concessions in exchange for a deal, and is calling for a Putin-Zelensky summit to break the deadlock.

Putin has effectively ruled that out, and has issued a threat to target any Western soldiers that might be sent to Kyiv as peacekeepers without his approval.