After initially trying to downplay a personal rivalry between himself and Putin, Biden has stepped up his rhetoric against Putin over the past 10 days. Last week, Biden first called Putin a “war criminal” and later described him as “a murderous dictator, a pure tramp who is waging an immoral war against the people of Ukraine.” He also called the Russian invasion of Ukraine “inhumane.” The US State Department officially announced on Wednesday that members of the Russian armed forces have committed war crimes in Ukraine. The decision to issue a formal indictment marked a major step by the US government after weeks of refusing to formally declare that attacks on civilians in Ukraine were war crimes. It remains to be seen, however, whether those accused of committing the alleged crimes will be held accountable and whether Putin himself will be held accountable. Biden’s latest remarks about Putin came as he focused on the refugee crisis in Europe as millions of people are fleeing their homes in Ukraine. The President met with Chef José Andrés and other volunteers in Warsaw at a food distribution site for Andrés’ World Center Kitchen, a non-profit organization dedicated to providing food in the aftermath of disasters. Biden met with some of the volunteers, others from Europe and others from the United States. “God loves you,” the President was heard saying to them and asking if he could help them. More than 3.5 million refugees have now fled Ukraine, according to data from the United Nations High Commissioner for Refugees (UNHCR) released on Tuesday. The vast majority of these refugees have taken refuge in Ukraine’s western neighbors throughout Europe. Poland, which borders Ukraine to the west, has recorded more than 2 million Ukrainian refugees crossing into the country, although not all of the refugees who have entered Poland remain there. During the short Q&A session, Biden recounted how he had gone to such places in his life, but said he was always surprised by “the depth and power of the human spirit.” “It’s unbelievable, it’s unbelievable. Look at all these little kids. I just want to hug, I just want to say thank you. I mean, it’s just makes you so proud,” he said. He added, “Each of these children said something about it: ‘Say a prayer for my dad or my grandfather or my brother who is back there fighting. And I remember what it’s like when you have someone in a war zone. Every morning you get up and wonder. You’re just wondering. And you pray that you do not receive this phone call. “ The Russian military’s advance seems to have stopped around major Ukrainian cities, such as Kyiv and Kharkiv, and a top Russian general says the first phase of their invasion is over, with the focus now shifting to eastern Ukraine. Russia has also failed to achieve air supremacy in Ukraine and has suffered heavy personnel losses since the invasion began. “In general, the main tasks of the first stage of the operation have been completed,” Colonel Sergei Rudskoi, Russia’s first deputy chief of staff, told a news conference on Friday. “The combat potential of the Ukrainian armed forces has been significantly reduced, allowing us, I reiterate, to focus our main efforts on achieving the main goal – the liberation of Donbass.” “I’m not sure they have changed,” Biden said when asked about the change in Russian military strategy in Ukraine. This story has been updated with additional references. CNN’s Nathan Hodge, Maegan Vazquez, Jennifer Hansler and Jeremy Herb contributed to this report.