Russian President Vladimir Putin will meet US special envoy Steve Witkoff in Moscow on Tuesday, after the White House said it was "very optimistic" about reaching a deal to end the Ukraine war.

US President Donald Trump's son-in-law Jared Kushner, who has acted as an outside adviser in diplomatic talks, is also expected to attend.

The summit comes after two days of negotiations in Florida between Ukrainian and US officials, including Witkoff and Kushner, aimed at refining a US-backed peace plan which had been viewed as favourable to Russia.

Ukrainian President Volodymyr Zelensky described the talks as "constructive", but said there were "some tough issues that still have to be worked through".

Witkoff's meeting with Putin will be during the second half of Tuesday, Kremlin spokesman Dmitry Peskov said.

Speaking after a meeting with French President Emmanuel Macron in Paris on Monday, Zelensky said Kyiv's priorities in peace talks were maintaining Ukraine's sovereignty and securing strong security guarantees.

Zelensky said the "territorial issue is the most difficult" element of the peace deal, with the Kremlin continuing to push for Ukraine to cede territory in the east which it still controls - something Kyiv has long-maintained it will never do.

The talks in Moscow on Tuesday come hours after Russian officials claimed to have captured the key strategic town of Pokrovsk in eastern Ukraine, known in Russian as Krasnoarmeysk, and the north-eastern Ukrainian border town of Vovchansk.

Ukrainian officials made no acknowledgement that either city had fallen to Russia and open-source intelligence projects monitoring the front lines of the war suggested neither Vovchansk nor Pokrovsk had yet been fully captured by the Russian army.

The head of Ukraine's centre for countering disinformation, Andriy Kovalenko, said it seemed Russia's main aim was to ensure all the pressure in the US peace plan was put on Ukraine.

Russia has spent almost a year and a half trying to capture Pokrovsk and released a video showing Putin visiting a command post at the weekend in which he was quoted as saying Russia has made progress in "an important area, we all understand just how important".

Ahead of his trip to Moscow, Witkoff also held talks with UK Prime Minister Sir Keir Starmer, Zelensky and Ukraine's new chief negotiator Rustem Umerov, while several key European leaders virtually joined the Zelensky-Macron meeting.

Speaking on Monday, White House Press Secretary Karoline Leavitt said the draft peace deal had "been very much refined", adding: "I think the administration feels very optimistic."

She continued: "But as for the details, I will let the negotiators negotiate. But we do feel quite good, and we're hopeful that this war can finally come to an end."

Last week, Putin said he had seen a draft peace plan proposed by the US, and that it could become the "basis" for a future agreement to end the war.

However, Kremlin officials later cast doubt over whether it would accept the proposal after Kyiv and European allies said they had secured changes to it.

The initial US-Russia draft peace plan circulated in November sparked consternation in Kyiv and around Europe.

As well as being heavily slanted towards Moscow's demands, it also dictated how several billion in frozen Russian assets currently held in European financial institutions should be invested, as well as setting the terms for Ukrainian market access in Europe.

Speaking on Monday, Macron said there was currently "no finalised peace plan to speak of", and insisted that any such proposal could only be worked out with input from Ukraine and Europe.

Macron said the question of territorial concessions could "only be finalised by President Zelensky", and pointed out that questions around frozen Russian assets, security guarantees, and Ukraine's accession to the EU needed to involve European nations.

The French leader also praised efforts by the Trump administration to end the conflict, which began in 2014 with Russia's illegal annexation of Crimea, followed by a full-scale invasion of Ukraine in 2022.

Kaja Kallas, the EU's foreign policy chief, said this week could be "pivotal", but that Moscow only wanted to negotiate "with those who are just offering them something on top of what they already have".

She continued: "I'm afraid all the pressure will be put on the weaker side because that is the easier way to stop this war when Ukraine surrenders, but this is not in anybody's interest."

In recent months Moscow has at times appeared to engage with US attempts to mediate an agreement to end the war, but several of its demands directly counter Ukraine's sovereignty and are seen as unacceptable by Kyiv.

While the question of territory is the major sticking point, the issue of security guarantees for Kyiv has also proved contentious.

Kyiv and its European partners are keen for Ukraine to be given security guarantees - such as Nato membership - that would protect it from being attacked again.

But Russia vehemently opposes this and Trump has also ruled out allowing Ukraine to join the military alliance.