Low-level delegations from Russia and Ukraine held their first direct peace talks in three years in Istanbul on May 16. The talks, which lasted two hours, brought no significant breakthrough, although both sides agreed to the largest prisoner exchange of the war. It was carried out last weekend and freed 1,000 captives on each side.

Ukraine said it will not send a delegation for peace talks to Istanbul Monday until Russia provides details of its cease-fire proposal. Ukraine accused Russia of stalling in peace negotiations.

With Russia saying its terms for peace must remain secret until the talks begin, Ukraine won’t confirm whether its delegation will even attend.