Ukraine resisted pressure from Russia and the United States to commit itself to attending peace talks with Russia on 2 June, saying it first needed to see the proposals Russian negotiators plan to bring to the talks.
After US President Donald Trump urged Russia and Ukraine to work together on a peace deal to end their three-year-old war, Russia proposed sitting down with Ukrainian officials next week in Istanbul.
Ukraine responded by saying it was committed to the search for peace, but that it was waiting for a memorandum from the Russian side setting out their proposals, which it had still not received.
"For a meeting to be meaningful, its agenda must be clear, and the negotiations must be properly prepared," Ukrainian President Volodymyr Zelensky wrote on X after hosting Turkey's foreign minister for talks in Ukraine.
"Unfortunately, Russia is doing everything it can to ensure that the next potential meeting brings no results," he said, citing the lack of a document from Russia.
The war, the biggest on the European continent since World War Two, began when Russia launched a full-scale invasion of Ukraine in February 2022.
Expectations for the talks are modest because the positions staked out so far by the two sides are far apart and work between them has yet to begin in earnest on narrowing the gap.
Nevertheless, both Ukraine and Russia are keen to demonstrate to Mr Trump that they are on board with his efforts to end the conflict. Ukraine is seeking more US military aid, while Russia hopes he will ease economic sanctions on Russia.
In Russia, Kremlin spokesman Dmitry Peskov said the Russian delegation would be travelling to Turkey and would be ready for talks with Ukraine on Monday morning.
"At the moment, everyone is focused on the direct Russia-Ukraine negotiations. A list of conditions for a temporary truce is being developed," Mr Peskov told reporters.
Reuters reported earlier this week that Russian President Vladimir Putin's conditions for ending the war in Ukraine include a demand that Western leaders pledge in writing to stop enlarging NATO eastwards.
Mr Trump's envoy to Ukraine, Keith Kellogg, said that Russia's concern over the eastward enlargement of NATO was fair and the United States did not want to see Ukraine in the US-led military alliance.
Commenting on Mr Kellogg's statement, Mr Peskov said, "We are pleased that these explanations by the president are understood, including in Washington."
Turkish hosts
Turkey's government hosted a previous round of Ukraine-Russia talks in Istanbul on 16 May - which ended with no breakthrough - and has again offered its services as a mediator.
Turkish Foreign Minister Hakan Fidan told reporters in Ukraine, "As long as (the sides) remain at the negotiating table, progress can surely be seen."
If the talks go ahead in Istanbul, the next step would be to try to host a meeting between Mr Trump, Mr Putin, and Mr Zelensky, he added.
But Ukrainian Foreign Minister Andrii Sybiha, who appeared alongside Mr Fidan at a news conference, said Ukraine needed to see the Russian proposals in advance for the talks to be "substantive and meaningful."
Mr Sybiha did not spell out what Ukraine would do if it did not receive the Russian document, or set out a deadline for receiving it.
"We want to end this war this year, and we are interested in establishing a truce, whether it is for 30 days, or for 50 days, or for 100 days," he said.
Russia has said its delegation at the Istanbul talks will be led by Vladimir Medinsky, a Kremlin aide who led the Russian team at the previous round of talks.
