US envoy Steve Witkoff arrived in Moscow on Thursday to present Washington's plan for a 30-day ceasefire in Ukraine, a source said, as the Kremlin warned against any "hasty" deal that would give Kyiv a respite from fighting.

Ukraine agreed to the plan during talks with US officials in Saudi Arabia on Tuesday, as US President Donald Trump pushes for a speedy end to the more than three-year conflict.

But even before meeting Witkoff, an aide to Russian President Vladimir Putin said the document only took Ukraine's position into account, and that Russia needed input as well.

"It will be necessary to work on it, think and take into account our position," Yuri Ushakov told Russian state TV, saying Putin would probably give his verdict on the deal later.

Kremlin aide Yuri Ushakov dismissed the ceasefire as "nothing but a temporary respite" for Ukraine. Photo: AFP

Russia has been grinding forward on the battlefield for over a year, and claimed on Thursday to have driven Ukrainian forces from the town of Sudzha in Russia's Kursk region.

Trump has expressed optimism that his team can secure a ceasefire, despite Moscow's battlefield gains.

"If we can get Russia to stop, then we have a full ceasefire. And I think it'll never go back to war," Trump told reporters on Wednesday.

Ukrainian President Volodymyr Zelensky on Thursday said the fact Russia was yet to respond officially to the idea showed it did not want peace.

"Regrettably, for more than a day already, the world has yet to hear a meaningful response from Russia to the proposals made," he said on social media.

"This once again demonstrates that Russia seeks to prolong the war and postpone peace for as long as possible."

'Temporary breather'

Setting out its red lines ahead of the talks, Russia ruled out foreign peacekeepers in Ukraine and raised the possibility of relief from sanctions imposed on it.

Moscow wants any settlement to be long-term and to secure its interests, rather than a temporary deal that would give Ukraine a "breather", Ushakov said.

"That is what we are striving for. A peaceful settlement that takes into account the legitimate interests of our country," he told a state TV reporter.

Ushakov called the 30-day ceasefire proposal a "hasty" plan that "is not in favour of a long-term settlement".

"It would be nothing more than a temporary breather for the Ukrainian military," he said following a call with US National Security Advisor Mike Waltz.

Russia has also ruled out accepting foreign peacekeepers in Ukraine as part of a ceasefire or long-term security guarantee for Kyiv.

That could go against an ask Ukraine has made of European allies to deploy military "contingents" on its territory once the conflict ends to protect against future attacks from Russia.

"It is absolutely unacceptable to us that army units of other states are stationed in Ukraine under any flag," Russian foreign ministry spokeswoman Maria Zakharova said in a briefing.

"Be it a foreign contingent and a military base... all this would mean the involvement of these countries in a direct armed conflict with our country."

Battle for Kursk

Russia, meanwhile, claimed rapid advances in the Kursk region -- where Kyiv launched a cross-border assault last August and has held territory since.

The Russian defence ministry said it had "liberated" Sudzha along with two other settlements in the border region.

Sudzha, home to around 5,000 people before the fighting, was the largest settlement Kyiv seized after it launched its shock assault into Russia.

The Kursk region was one of Kyiv's few bargaining chips in swapping land with Russia, which has occupied around a fifth of Ukraine since it took Crimea in 2014 and launched its full-scale assault in February 2022.

Ukraine now risks losing its grip on the border region entirely, ceding dozens of square kilometres (miles) in the past seven days, according to military bloggers.

Ukraine's commander-in-chief hinted late Wednesday some of its troops were pulling back in the region.

Putin visited the region on Wednesday for the first time since Ukraine launched its incursion.

Dressed in battle fatigues, he expressed hope his army would "fully liberate" areas under Kyiv's control.

Moscow's rapid advances in the region came after the US paused intelligence sharing and security support for Ukraine, although analysts and officials cautioned against making a direct link.

Washington said it had resumed its support for Kyiv ahead of the talks with Moscow.

Both Moscow and Kyiv kept up hostilities into Thursday.

Russia downed 77 Ukrainian drones overnight, its defence ministry said, while Ukraine's air force said it downed dozens of drones fired at multiple regions.