CHERNIHIV REGION, Ukraine (AP) — A major prisoner exchange between Russia and Ukraine began Friday, a senior Ukrainian official said, in one of the few signs of progress from their direct talks last week in Istanbul — part of a U.S.-led effort that so far has failed to produce a ceasefire in the 3-year-old war.

The swap was taking place at the border with Belarus in northern Ukraine, according to the Ukrainian official who spoke on condition of anonymity because he was not authorized to speak publicly,

Moscow did not immediately confirm the exchange was underway.

Ukraine and Russia agreed to the exchange of 1,000 prisoners from each side a week ago in Turkey in their first direct peace talks since the early weeks of Moscow’s 2022 invasion of its neighbor. That meeting lasted only two hours and brought no breakthrough in efforts to stop the fighting.

Word of the developments emerged when U.S. President Donald Trump said Russia and Ukraine had carried out a large exchange of prisoners.

“A major prisoners swap was just completed between Russia and Ukraine,” Trump said on the Truth Social platform. He said it would “go into effect shortly,” although it was not clear what that meant.

“This could lead to something big???” Trump added in his post, apparently referring to international diplomatic efforts to stop the fighting.

White House and National Security Council officials did not immediately respond to requests for further details.

After the May 16 talks, Turkish Foreign Minister Hakan Fidan called the prisoner swap a “confidence-building measure” and said the parties had agreed in principle to meet again.

But Kremlin spokesman Dmitry Peskov said Friday that there has been no agreement yet on the venue for the next round of talks as diplomatic maneuvering continued.

European leaders have accused Russian President Vladimir Putin of dragging his feet in peace efforts while he tries to press his larger army’s battlefield initiative and capture more Ukrainian land.

The Istanbul meeting revealed both sides clearly remained far apart on key conditions for ending the fighting. One such condition for Ukraine, backed by its Western allies, is a temporary ceasefire as a first step toward a peaceful settlement.

The Kremlin has pushed back on a temporary halt to hostilities, and Putin has said any such truce must come with a freeze on Western arms supplies to Ukraine and an end to Ukraine’s mobilization drive.

A senior Ukrainian official said that in Istanbul, Russia had introduced new, “unacceptable demands” to withdraw Ukrainian forces from huge swaths of territory. The official, who was not authorized to make official statements, spoke to the AP on condition of anonymity. The proposal had not been previously discussed, the official said.

Putin has long demanded as a key condition for a peace deal that Ukraine withdraw its troops from the four regions that Russia annexed in September 2022 but never fully controlled.

Ukrainian President Volodymyr Zelenskyy has warned that if Russia continues to reject a ceasefire and make “unrealistic demands,” it will signal deliberate efforts to prolong the war — a move that should bring tougher international sanctions.

Fighting has continued along the roughly 1,000-kilometer (620-mile) front line, where tens of thousands of soldiers have been killed, and neither country has relented in its deep strikes.

Russia’s Ministry of Defense said Friday that it had shot down 788 Ukrainian drones away from the battlefield between May 20-23.

Ukraine’s air force said Russia fired 175 Shahed and decoy drones, as well as a ballistic missile since late Thursday.

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Arhirova reported from Kyiv, Ukraine. Associated Press writer Aamer Madhani in Washington contributed.

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Follow AP’s coverage of the war in Ukraine at https://apnews.com/hub/russia-ukraine