Ukrainian President Volodymyr Zelensky has said he will travel to Turkey's capital, Ankara, to meet President Recep Tayyip Erdogan and will be available for direct talks with his Russian counterpart, Vladimir Putin, in Istanbul on Thursday.

"We will do everything to ensure that this meeting takes place," he told reporters in a hastily arranged briefing in Kyiv.

Russia has not yet said who will fly to Istanbul, only that it would be announced "as soon as [Putin] deems it necessary". Putin and Zelensky have not met since December 2019.

Direct talks between the two countries last took place in Istanbul in March 2022, in the early weeks of Russia's full-scale invasion of Ukraine.

Putin had initially called for direct talks in Turkey's largest city "without pre-conditions", before Zelensky announced that he would go in person and expected the Russian president to travel as well.

The US is also expected to send a high-level delegation.

By confirming his visit to Turkey at Tuesday's briefing, Zelensky clearly sought to intensify pressure on Russia to respond. The Kremlin has already warned that exerting pressure on Moscow is "useless" and it does not respond to ultimatums.

Russia has instead sought to focus on a long-term settlement that tackles what Moscow sees as the "root causes" of the war - a set of tough pre-conditions announced before the 2022 invasion and repeatedly rejected by Kyiv.

The Ukrainian leader said while he was prepared to meet Putin in Istanbul, his priority was to secure a 30-day ceasefire, which he said all Ukraine's allies - including the US - were agreed on.

Zelensky said he believed Putin's late-night offer on Sunday for direct talks in Turkey was designed to catch Kyiv out, so that he would "not react" or "react in a negative way for Ukraine".

US President Donald Trump, who is on a visit to the Gulf, has hinted that he could fly to Istanbul himself "if I think things can happen".

That seems unlikely for now, and unconfirmed reports suggest two senior US envoys, Steve Witkoff and Keith Kellogg, are planning to be in Istanbul on the day.

The Kremlin has sought to dampen speculation that Putin himself might go.

"Russia continues preparations for the negotiations due on Thursday. That's all that can be said right now," said Kremlin spokesman Dmitry Peskov.

Deputy Foreign Minister Sergei Ryabkov said on Tuesday that Moscow was prepared to hold talks "responsibly" taking into account "realities on the ground" - in a veiled reference to Ukraine's four south-eastern regions partially seized by Russia since 2022.

He also repeated Moscow's initial pre-invasion demands for a settlement to be achieved - Ukraine and its Western allies see this as an ultimatum tantamount to Kyiv's de facto capitulation.

Ryabkov also cast doubt on Ukraine's ability to stick to agreements.

EU foreign policy chief Kaja Kallas said it would be a good move for Zelensky and Putin to sit down and talk, but added, "I don't think he dares, Putin."

Zelensky also accused Putin of "being scared" to meet him. His chief of staff, Andriy Yermak, said if the Russian leader refused to go to Istanbul, it would be the "final signal" that he did not want to end the war.

The leaders of Ukraine's main allies - the UK, Germany, Poland and France - travelled to Kyiv at the weekend to warn of immediate further sanctions if Russia did not accept a 30-day ceasefire.

The European Union is currently working on a 17th package of measures.