KYIV, Ukraine — Russia pressed Thursday for the West to lift sanctions imposed because of its war in Ukraine, claiming without proof that the punitive measures are preventing millions of tons of grain and other agricultural products from leaving Ukrainian ports, exacerbating a global food crisis.

Ukraine is one of the world’s largest exporters of wheat, corn and sunflower oil, but the war, including a Russian blockade of its ports, has prevented most of those products from leaving the country, endangering the world food supply.

But Kremlin spokesman Dmitry Peskov sought to shift the blame to Western sanctions on Thursday. “We accuse Western countries of taking a series of unlawful actions that has led to the blockade.”

Western officials have dismissed Russia’s claims that sanctions are responsible. U.S. Secretary of State Antony Blinken noted this week that food, fertilizer and seeds are exempt from sanctions imposed by the U.S. 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 ramped up calls for solutions this week.

“This food crisis is real, and we must find solutions,” World Trade Organization Director-General Ngozi Okonjo-Iweala said at the World Economic Forum meeting in Davos, Switzerland, on Wednesday. “If we don’t find solutions, of course the countries that will suffer will be the poorer countries of the world.”

She said about 25 million tons of Ukrainian grain is presently in storage and another 25 million tons could be harvested next month.

The Russian Defense Ministry proposed Wednesday to open a corridor to allow foreign ships to leave Black Sea ports and another to allow vessels to leave Mariupol on the Azov Sea. But Russia said the Mariupol port in particular had to be cleared of mines first. Ukraine expressed skepticism about that proposal.

Speaking in Davos, Switzerland, Ukrainian Foreign Minister Dmytro Kuleba said Ukraine was ready to agree on safe corridors in principle — but that it was not sure if it could trust Russia to abide by any agreement.

The issue, he said, was “how to guarantee that the moment we will create this safe passage and the entry to the harbor is demined, how to make sure that at night or early in the morning, Russia will not violate the agreement on the safe passage and its military vessels will not sneak into the harbor and attack Odesa.”

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

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

On the battlefield, the General Staff of the Ukrainian military said Thursday that the Russian forces continued attempts to press their offensive in several sections of the frontline Ukraine’s eastern Donbas region. That industrial heartland of coal mines and factories is now the focus of fighting after Russia suffered a series of setbacks and war forced to pursue more limited goals.

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

They also said Russia also launched missile and airstrikes at infrastructure facilities across the country.