Jill Biden Received Letter from Ukrainian First Lady with Country's Needs: 'We're Working on It'

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Dr. Jill Biden is bringing aid to the people of Ukraine and Eastern Europe this Mother's Day.

During a preview of her interview with MSNBC's Symone Sanders, airing Saturday, the first lady said that she received a letter from Ukrainian First Lady Olena Zelenskyy with "her list of things that they needed."

"They need so much. They have so many children without parents, so many orphans that need childcare, that need clothing, that need health supplies. They need food," Biden, 70, said. "I mean, they need so much. And so, she gave me a list and we're working on it."

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She also had a phone call with Polish First Lady Agata Kornhauser-Duda ahead of her trip, during which she will spend the holiday with displace Ukrainian families.

"I knew Mother's Day was coming up and I said to Joe, 'I'm going to go stand with the mothers of Ukraine. They have to know that we're standing with them,' " she recalled to Sanders in the preview. "Because I don't know about you, Symone, but when I see those mothers with all their children, they are so resilient.

Chris McGrath/Getty Evacuees Arrive In Zaporizhzhia

"And you just wonder, don't you? You ask yourself, 'Could I do that? Could I leave my country, my husband, everybody I love and move on to something unknown. ... So I will be there on Mother's Day standing with the mothers of Ukraine," Biden said.

She announced this week that she'll visit Romania and Slovakia for five days as she meets with U.S. service members, embassy personnel, humanitarian aid workers and Ukrainians displaced amid the Russian invasion.

"I think that they have shown us so much strength and they've been my inspiration, really. Because if they can be strong, then I can be strong for them," Biden said in the preview of her MSNBC interview. "So, I hope I bring strength. ... I hope that they know that I have the hearts of everyone in the United States, I'm carrying the United States with me to say we're standing with you."

Russia's attack on Ukraine continues after their forces launched a large-scale invasion on Feb. 24 — the first major land conflict in Europe in decades.

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Details of the fighting change by the day, but thousands of civilians have already been reported dead or wounded, including children. Millions of Ukrainians have also fled, the United Nations says.

"You don't know where to go, where to run, who you have to call. This is just panic," Liliya Marynchak, a 45-year-old teacher in Ivano-Frankivsk, Ukraine, told PEOPLE of the moment her city was bombed — one of numerous accounts of bombardment by the Russians.

The invasion, ordered by Russian President Vladimir Putin, has drawn condemnation around the world and increasingly severe economic sanctions against Russia.

RELATED VIDEO: As Russia's Invasion of Ukraine Continues, Citizens Around the World Still Manage to Uplift Each Other

With NATO forces massing in the region around Ukraine, various countries have also pledged aid or military support to the resistance. Ukrainian President Volodymyr Zelenskyy called for peace talks — so far unsuccessful — while urging his country to fight back.

Putin, 69, insists Ukraine has historic ties to Russia and he is acting in the best security interests of his country. Zelenskyy, 44, vowed not to bend.

"Nobody is going to break us, we're strong, we're Ukrainians," he told the European Union in a speech in the early days of the fighting, adding, "Life will win over death. And light will win over darkness."

The Russian attack on Ukraine is an evolving story, with information changing quickly. Follow PEOPLE's complete coverage of the war here, including stories from citizens on the ground and ways to help.