Washington DC - President Donald Trump on Friday announced a "major" prisoner swap between Ukraine and Russia, teasing the possibility of greater things to come in the push to end the conflict.

"A major prisoners swap was just completed between Russia and Ukraine," Trump wrote on his Truth Social platform.

"Congratulations to both sides on this negotiation. This could lead to something big???" he said, without providing further details.

His announcement follows Moscow and Kyiv agreeing during talks in Istanbul this month to exchange 1,000 prisoners each.

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The warring countries have held many rounds of swaps since Russia launched its full-scale invasion of Ukraine in February 2022.

In an exchange earlier this month, the two sides each released 205 captured soldiers.

Separately, the Kremlin said this week that Russian President Vladimir Putin and Trump discussed a bilateral prisoner swap with the US.

The Republican's push for an immediate ceasefire has been rebuffed by Putin so far, and Moscow's announcement on Thursday that it was constructing a "buffer zone" on its border with Ukraine added to the sense that a resolution to the war is still far off.