EU leaders have asked Vladimir Putin to have “direct [and] serious negotiations” with Ukraine’s president.
The German chancellor’s office said Emmanuel Macron and Olaf Scholz “insisted on an immediate ceasefire and a withdrawal of Russian troops” in an 80-minute phone call.
Meanwhile, Mr Putin is open to resuming dialogue with Kyiv, the Kremlin said following the call.
It comes as Ukrainian and Russian delegations have undergone numerous rounds of talks both in person and virtually since the invasion first started on February 24.
The pair also pressed on the issue of the release 2,500 Ukrainian fighters, who have been taken as prisoners of war at the Azovstal steelworks in Mariupol.
Last week, the Russian military declared Azovstal and the besieged port southern city “completely liberated”, saying that the fighters had left the last site of Ukrainian resistance there.
It comes as Russian forces stepped up their assault on Sievierodonetsk on Saturday, after claiming to have captured the nearby rail hub of Lyman in eastern Ukraine.
Russia’s defence ministry said on Saturday its troops and allied separatist forces were now in full control of Lyman, the site of a railway junction west of the Siverskyi Donets River in the Donetsk region that neighbours Luhansk.
Meanwhile, Ukraine’s foreign minister Dmytro Kuleba said Western sanctions on Russia have “no connection” to the unfolding world food shortage.
In a statement on Twitter, Mr Kuleba said: “Sanctions on Russia have no connection to the unfolding global food crisis.
“The sole reason for shortages, rising prices, and threat of hunger is the Russian military physically blocking 22 million tonnes of Ukrainian food exports in our seaports.
“Demand Moscow to end its blockade.”
Russia and Ukraine are huge exporters of some of the world’s biggest staple foods and between them are responsible for 53% of global trade in sunflower oil and seeds and 27 per cent of the wheat trade, according to the UN Conference on Trade and Development.
At the moment, Ukraine has vast quantities of wheat in storage that, because of the war, it is unable to export.
Moscow and Kyiv have traded blame over which is responsible for keeping shipments tied up, with Russia saying Ukrainian sea mines prevented safe passage.
Ukrainian forces may have to retreat from their last pocket of resistance in Luhansk to avoid being captured, the region’s governor has said.
Defending troops are being forced to retreat in parts of the country’s eastern region where Moscow has shifted its focus.
Donbas is the home of the so-called People’s Republics of Donetsk and Luhansk, which Russia claims on behalf of separatists.
Russia's defence ministry claimed on Saturday the Ukrainian town of Lyman had fallen under the full control of Russian and Russian-backed forces in eastern Ukraine.
Invading forces are said to have now entered the city of Sievierodonetsk in Luhansk.
Governor of Luhansk Serhiy Gaidai remained adamant that the Russians will not be able to capture the region “as analysists have predicted”.
"We will have enough strength and resources to defend ourselves. However, it is possible that in order not to be surrounded we will have to retreat," Gaidai said on Telegram.
He said 90 per cent of buildings in Sievierodonetsk were damaged with 14 high-rises destroyed in the latest shelling.
Speaking to Ukrainian television, Gaidai said there were some 10,000 Russian troops based in the region and they were "attempting to make gains in any direction they can".
He said several dozen medical staff were staying on in Sievierodonetsk but they faced difficulty just getting to hospitals because of the shelling.
President Volodymyr Zelensky said Ukraine was protecting its land "as much as our current defence resources allow".
Ukraine’s military said it had repelled eight attacks in Donetsk and Luhansk on Friday, destroying tanks and armoured vehicles.
"If the occupiers think that Lyman and Sievierodonetsk will be theirs, they are wrong. Donbas will be Ukrainian," Zelensky said in an address.
Gaidai said: "It is clear that our boys are slowly retreating to more fortified positions - we need to hold back this horde."
Separately, senior Ukrainian military official Gen Oleksiy Gromov conceded at a briefing earlier this week that the invading forces had the upper hand in Luhansk.
It comes after Boris Johnson warned Vladimir Putin’s troops were making “palpable progress” in the Donbas region of Ukraine.
The Russian army have been accused of “pounding residential neighbourhoods relentlessly” during an operation to seize two key cities in the industrial east of Ukraine.
Now the Prime Minister said the Ukrainians had showed “incredible heroism” in pushing the Russians back from the capital Kyiv but it had caused Putin to focus all of his military might on seizing the Donbas.
“I’m afraid that Putin, at great cost to himself and to Russian military, is continuing to chew through ground in Donbas,” the Prime Minister told Bloomberg TV.
“He’s continuing to make gradual, slow but, I’m afraid, palpable progress and therefore it is absolutely vital that we continue to support the Ukrainians militarily.”
