President Joe Biden on Saturday marveled at the spirit and resolve of of Ukrainian refugees in the aftermath of Russia’s deadly invasion as he embraced mothers and children and promised enduring support from Western powers.

Biden, while in Poland’s capital, listened intently as children described the perilous flight from neighboring Ukraine with their parents. Smiling broadly, he lifted up a young girl in a pink coat and told her she reminded him of his granddaughters. The president held hands with parents and gave them hugs during the stop at a soccer stadium where refugees go to obtain a Polish identification number that gives them access to social services such as health care and schools,

Some of the women and children told Biden that they fled without their husbands and fathers, men of fighting age who were required to remain behind to aid the resistance against the forces that Russian President Vladimir Putin — “a butcher,” in Biden’s words — sent into Ukraine more than a month ago.

“What I am always surprised by is the depth and strength of the human spirit,” Biden told reporters after his conversations with the refugees at the stadium, which more recently had served as a field hospital for COVID-19 patients. “Each one of those children said something to the effect of, ’Say a prayer for my dad or grandfather or my brother who is out there fighting.”

The president, who was set to return to Washington later in the day, tried to use his final hours of his European trip reassuring Poland that the United States would defend against any attacks by Russia as he acknowledged that the NATO ally bore the burden of the refugee crisis from the war.

Before leaving Poland, Biden was to deliver an address expected to focus on the difficult path ahead as U.S. and Western allies continue to assist Ukraine and prod Russia to end its invasion.

“Your freedom is ours,” Biden told Poland’s president, Andrzej Duda earlier, echoing one of that country’s unofficial mottos.

At the Presidential Palace in Warsaw, the two leaders spoke of their mutual respect and shared goals to end the Russian invasion of Ukraine.

“Although times are very difficult, today Polish-American relations are flourishing,” Duda said.

More than 3.7 million people have fled Ukraine since the war began, and more than 2.2 million Ukrainians have crossed into Poland, though it is unclear how many have remained there and how many have left for other countries. Earlier this week the U.S. announced it would take in as many as 100,000 refugees, and Biden told Duda that he understood Poland was “taking on a big responsibility, but it should be all of NATO’s responsibility.”

Biden called the “collective defense” agreement of NATO a “sacred commitment,” and said the unity of the Western military alliance was of the utmost importance.

“I’m confident that Vladimir Putin was counting on dividing NATO,” Biden said. “But he hasn’t been able to do it. We’ve all stayed together.”

European security is facing its most serious test since World War II. Western leaders have spent the past week consulting over contingency plans in case the conflict spreads. The invasion has shaken NATO out of any complacency it might have felt and cast a dark shadow over Europe.

Biden’s national security adviser, Jake Sullivan, said Biden’s speech would outline the “urgency of the challenge that lies ahead” and “what the conflict in Ukraine means for the world, and why it is so important that the free world stay in unity and resolve in the face of Russian aggression.”

In addition to the meeting with Duda, Biden attended a meeting of American and Ukrainian diplomatic and defense officials for an update on Ukraine’s military, diplomatic and humanitarian situation.

Warsaw, a city of nearly 1.8 million people, has grown by about 17% in a month as the refugees have come in huge numbers seeking shelter.

While Poles have so far welcomed Ukrainians, the humanitarian efforts are largely the work of volunteers. Warsaw Mayor Rafal Trzaskowski has warned it is not sustainable and that social services are buckling under the strain.

The U.S. has been sending money and supplies to aid the refugee effort. This week, Biden announced $1 billion in additional aid in addition to accepting refugees.

The U.S. and many of its allies have imposed multiple rounds of economic and other sanctions on Russian individuals, banks and other entities in hopes that the cumulative effect over time will force Putin to withdraw his troops.

(AP)