(Reuters) -Ukraine's defence minister recently had a call with the head of the Russian delegation in the Istanbul talks, President Volodymyr Zelenskiy said on Wednesday, in order to discuss the memorandum Moscow is currently working on laying out its conditions for any peace accord.

Defence Minister Rustem Umerov led the Ukrainian delegation to the May 16 talks, the first between the warring nations since spring 2022. The Russian team was led by Vladimir Medinsky.

Kyiv and its allies have pushed Russia for an immediate and unconditional ceasefire as a basis for talks to end the conflict, while Moscow says that it has certain conditions which must first be met, and which it has said it will lay out.

Zelenskiy, speaking in Berlin, said that Russia was persistently searching for reasons to delay talks to end the war, which has ground on for over three years.

"The world has been waiting for more than a week for the Russians to complete their so-called memorandum on what they need to stop the killing of people," he said.

The Ukrainian leader said earlier that Kyiv was still waiting for Moscow to produce a memorandum on how it saw the future of peace talks before it could respond.

He said Ukraine had contacted the Russian side after the Istanbul talks, in which Russia first said it would produce the memorandum, to ask about the document.

"Our side - we were in touch with the Russians. The Minister of Defence called Russia's Medinsky. They said it would happen. But we never got it," Zelenskiy said, adding that the U.S. had not received anything either.

Kremlin spokesman Dmitry Peskov said on Wednesday Russia was preparing for the next round of negotiations with Ukraine and to continue contacts with the United States.

Istanbul could be a venue for the next round of negotiations, Peskov said.

(Reporting by Yuliia Dysa, Writing by Max Hunder;Editing by Alison Williams and Ros Russell)