Moscow pressed the West on Thursday to lift sanctions against Russia over the war in Ukraine, seeking to shift the blame for a growing food crisis that has been worsened by Kyiv’s inability to ship millions of tons of grain and other agricultural products while under attack.

Britain immediately accused Russia of “trying to hold the world to ransom,” insisting there would be no sanctions relief, and a top US diplomat blasted the "sheer barbarity, sadistic cruelty and lawlessness” of the invasion.

Russian President Vladimir Putin told Italian Prime Minister Mario Draghi that Moscow “is ready to make a significant contribution to overcoming the food crisis through the export of grain and fertilizer on the condition that politically motivated restrictions imposed by the West are lifted," according to a Kremlin readout of the call.

Ukraine is one of the world’s largest exporters of wheat, corn and sunflower oil, but the war and a Russian blockade of its ports have halted much of that flow, endangering world food supplies. Many of those ports are now also heavily mined.

Russia also is a significant grain exporter, and Kremlin spokesman Dmitri Peskov said the West “must cancel the unlawful decisions that hamper chartering ships and exporting grain.” His comments appeared to be an effort to lump the blockade of Ukrainian exports with what Russia says are its difficulties in moving its own goods.

Western officials have dismissed those claims. US Secretary of State Antony Blinken noted last week that food, fertilizer and seeds are exempt from sanctions imposed by the US and many others – and that Washington is working to ensure countries know the flow of those goods should not be affected.

With the war grinding into its fourth month, world leaders have ramped up calls for solutions. World Trade Organisation Director-General Ngozi Okonjo-Iweala said about 25.4 million tonnes of Ukrainian grain is in storage and another 25.4 million tonnes could be harvested next month.

European countries have tried to ease the crisis by moving grain out of the country by rail – but trains can carry only a small fraction of what Ukraine produces, and ships are needed for the bulk of the exports.

At the same time, the Russian Defence Ministry proposed corridors to allow foreign ships to leave ports along the Black Sea, as well as Mariupol on the Sea of Azov.

READ MORE

• 'New world order': Bizarre letter reveals Putin's terrifying plan
• NZ’s foreign policy turnaround: New Australian Govt will peg back tensions
• Russian parliament passes bill allowing Moscow to shut down 'unfriendly' foreign media
• Foreign Affairs Minister Nanaia Mahuta hasn't directly spoken with NZ's Ambassador to Russia since Ukraine invasion began

Mikhail Mizintsev, who heads Russia’s National Defence Control Centre, said 70 foreign vessels from 16 countries were in six ports on the Black Sea, including Odesa, Kherson and Mykolaiv. He did not specify how many might be ready to carry food.

Ukrainian Foreign Minister Dmytro Kuleba said his country was ready to agree on safe corridors in principle, but it was not sure it could trust Russia to allow safe passage and not send its military vessels “sneaking” into the harbour to attack Odesa.

British Foreign Secretary Liz Truss said Putin was “trying to hold the world to ransom” by demanding some sanctions be lifted before allowing Ukrainian grain shipments to resume.

“He’s essentially weaponized hunger and lack of food among the poorest people around the world,” Truss said on a visit to Sarajevo, Bosnia-Herzegovina. "What we cannot have is any lifting of sanctions, any appeasement, which will simply make Putin stronger in the longer term”.

Ukrainian President Volodymyr Zelenskyy called for imposing even tougher sanctions on Russia, including for the European Union to ban Russian oil and gas.

“Pressuring Russia is literally a matter of saving lives,” he said in his nightly video address. “And every day of delay, weakness, various disputes or proposals to appease the aggressor at the expense of the victim is new Ukrainians killed. And these are new threats to everyone on our continent.”

Putin said “it’s impossible, utterly unrealistic in the modern world” to isolate Russia. Speaking via video to members of the Eurasian Economic Forum, which is comprised of several ex-Soviet nations, he said those who try would “primarily hurt themselves,” citing broken food supply chains.

Michael Carpenter, the US ambassador to the Organisation for Security and Cooperation in Europe, urged its members to provide Ukraine with what it needs to defend itself against Putin’s “revanchist delusions”.

If Russia achieved “success” in Ukraine, “there would be more horrific reports from filtration camps, more forcibly displaced people, more summary executions, more torture, more rape, and more looting,” Carpenter said in Vienna.

On the battlefield, Russian forces pressed their offensive in several parts of the eastern Donbas region, Ukraine's military said. That industrial heartland of coal mines and factories is now the focus of fighting after Russia suffered a series of setbacks and shifted to more limited goals.

“The enemy is storming the position of our troops simultaneously in several directions,” said Ukrainian Deputy Defence Minister Hanna Maliar. “We have an extremely difficult and long stage of fighting ahead of us”.

Kharkiv, Ukraine's second-largest city, also came under renewed shelling on Thursday. Zelenskyy said at least nine people were killed and 19 wounded. Among those killed were a five-month-old baby and its father, and the mother was in serious condition.

Military officials said Russian forces continued to try to gain a foothold in the area of Sievierodonetsk, the only part of the Luhansk region in the Donbas under Ukrainian government control.

A senior US defence official said Russia is making incremental progress in the Donbas, with fighting cantered on towns and villages as Russian and Ukrainian forces trade control over scraps of land. The official, who spoke on condition of anonymity to discuss the US military assessment, said those smaller artillery duels could be prolonged.

Russia has 110 battalion tactical groups, each with 800 to 1000 troops, committed to Ukraine, amounting to 80% of Moscow's total force, the official said, adding that it has lost 1000 tanks and three dozen fighter jets and other fixed-wing aircraft.

Zelenskyy pleaded with the West to send multiple launch rocket systems to Ukraine as soon as possible to give it a fighting chance against the Russian offensive in the Donbas.