Ukraine war live updates: Russia is preparing a new summer offensive against Ukraine, Zelenskyy says; China slams sanctions threat

This is CNBC's live blog tracking developments on the war in Ukraine. See below for the latest updates. 

Russia is preparing a new offensive against Ukraine that could begin in early summer, Ukrainian President Volodymyr Zelenskyy said Sunday.

Ukraine denied it is at the weakest point in the war since Russia almost captured Kyiv nearly two years, telling NBC that this is the most difficult time in terms of unity.

"I don't think that now it's the weakest moment," Zelenskyy told NBC Sunday, a day after the second anniversary of Russia's invasion of Ukraine.

"The weakest, or rather, [the most] shocking moment was on February 24, two years ago. Now is the hardest moment for our unity. If we all split, both externally with the partners, and God forbid, internally, then it would be the weakest moment. It hasn't happened yet," Zelenskyy said during a news conference in Kyiv Sunday. He said 31,000 Ukrainian soldiers have been killed since Russia's invasion two years ago.

Kusti Salm, permanent secretary of the Estonian Ministry of Defense, discusses the need to increase defense spending for Ukraine.

— Holly Ellyatt

Russian opposition politician Alexei Navalny was close to being freed in a prisoner swap at the time of his death, Maria Pevchikh, a Navalny ally, said on Monday.

Speaking on YouTube, Pevchikh — who alleges the Russian authorities murdered Navalny, something they deny — said Navalny and two U.S. nationals were in line to be exchanged for Vadim Krasikov, a Russian FSB security service hit man who is serving a life sentence in Germany.

— Reuters

Russian President Vladimir Putin will meet with his Turkish counterpart, President Recep Tayyip Erdogan, after the Russian presidential election in mid-March, the Kremlin said