Russia said on Wednesday that a neutral Ukraine with its own army along the lines of Austria or Sweden was being looked at as a possible compromise in peace talks with Kyiv.

"This is a variant that is currently being discussed and which could really be seen a compromise," Kremlin spokesman Dmitry Peskov was quoted as saying by RIA news agency.

He was speaking nearly three weeks after Russia invaded Ukraine on February 24, in what it calls a special military operation.

Peskov was commenting on remarks from Vladimir Medinsky, Russia's chief negotiator, who earlier told state TV: "Ukraine is offering an Austrian or Swedish version of a neutral demilitarized state, but at the same time a state with its own army and navy.

Ukraine has not confirmed it is willing to discuss neutrality. It says it is ready to negotiate to end the war, but not to surrender or accept Russian ultimatums

A Ukrainian negotiator said a model of legally binding security guarantees that would offer Ukraine protection from a group of allies in the event of a future attack was "on the negotiating table".

"What does this mean? A rigid agreement with a number of guarantor states undertaking clear legal obligations to actively prevent attacks," negotiator Mykhailo Podolyak said on Twitter

Officials on both sides have made cautiously positive statements in recent days on progress towards a possible agreement after three weeks of war that have killed thousands of people and displaced several million Ukrainians.

"Neutral status is now being seriously discussed along, of course, with security guarantees," Russian Foreign Minister Sergei Lavrov told RBC news earlier on Wednesday.

"Now this very thing is being discussed in negotiations - there are absolutely specific formulations which in my view are close to agreement," Lavrov said.

Austria, which Russia is now citing as a potential model, is bound to neutrality by its constitution, which prohibits entry into military alliances and the establishment of foreign military bases on its territory.

Russia and Ukraine both emphasised new-found scope for compromise on Wednesday as peace talks resumed three weeks into a Russian assault that has so far failed to topple the Ukrainian government.

Ukraine's President Volodymyr Zelensky said the talks were becoming "more realistic", while Russian Foreign Minister Sergei Lavrov said there was "some hope for compromise", with neutral status for Ukraine - a major Russian demand - now on the table.

Three weeks into the invasion, Russian troops have been halted at the gates of Kyiv, having taken heavy losses and failed to seize any of Ukraine's biggest cities in a war Western officials say Moscow thought it would win within days.

Ukrainian officials have expressed hope this week that the war could end sooner than expected - even within weeks - as Moscow was coming to terms with a lack of fresh troops to keep fighting.

Talks resumed on Wednesday by video link for what would be a third straight day, the first time they have lasted more than a single day, which both sides have suggested means they have entered a more serious phase.

"The meetings continue, and, I am informed, the positions during the negotiations already sound more realistic. But time is still needed for the decisions to be in the interests of Ukraine," Zelenskiy said in a video address overnight.

On Tuesday, Zelensky had hinted at a possible route for compromise, suggesting Ukraine would be willing to accept international security guarantees that stopped short of its longstanding hope for full admission to the NATO alliance.

Keeping Ukraine out of NATO was long one of Russia's main demands, in the months before it launched what it calls a "special operation" to disarm and "denazify" Ukraine.

"The negotiations are not easy for obvious reasons," Lavrov told media outlet RBC news. "But nevertheless, there is some hope of reaching a compromise."

"Neutral status is now being seriously discussed along, of course, with security guarantees," Lavrov said. "Now this very thing is being discussed in negotiations - there are absolutely specific formulations which in my view are close to agreement."

Kremlin spokesman Dmitry Peskov said a demilitarised Ukraine with its own army, along the lines of Austria or Sweden, was being looked at as a potential compromise. They are the biggest of six EU countries that are outside NATO.

"This is a variant that is currently being discussed and which could really be seen a compromise," Peskov was quoted as saying by RIA news agency.

The head of Ukraine's negotiating team, Zelensky's aide Mykhailo Podlolyak, tweeted ahead of Wednesday's resumption of talks that Ukrainian military counteroffensives had "radically changed the parties' dispositions".