Moscow, Russia - Russian President Vladimir Putin held "constructive" talks with US envoy Steve Witkoff in Moscow on Wednesday, the Kremlin said, two days ahead of a US deadline for Russia to halt its Ukraine offensive or face fresh sanctions.

US President Donald Trump, who had boasted he could end the conflict within 24 hours of taking office, has given Russia until Friday to make progress towards peace or face new penalties.

But three rounds of Russia-Ukraine talks in Istanbul have failed to make headway on a ceasefire, with the two sides far apart in their demands.

Russia has escalated drone and missile attacks against its pro-Western neighbor to a record high and accelerated its advance on the ground.

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"A quite useful and constructive conversation took place," Putin's aide Yuri Ushakov told journalists, including AFP, after the three-hour meeting.

Putin and Witkoff exchanged "signals" on their positions, Ushakov said, without elaborating.

The Kremlin released a video of Putin shaking hands with Witkoff at the start of the meeting.

Ahead of the talks, Ukrainian President Volodymyr Zelensky urged Washington to increase its pressure on Moscow to agree to a ceasefire.

The White House has not outlined what action it would take against Russia, but Trump has previously threatened to impose "secondary tariffs" targeting Russia's key trade partners, such as China and India.

The move would aim to stifle Russian exports, but would risk significant international disruption.

Trump said on Tuesday that he would await the outcome of the Moscow talks before ordering any economic sanctions.

"We're going to see what happens," he told reporters. "We'll make that determination at that time."

Without explicitly naming Trump, the Kremlin on Tuesday slammed "threats" to hike tariffs on Russia's trading partners as "illegitimate."