(WASHINGTON) — As Ukrainians continue to flee their homes and find safety in neighboring countries, some cities are becoming overwhelmed with refugees and are unable to provide them with the resources they need.

“We’ll continue helping. We will accept as many Ukrainians as we need to,” Rafal Trzaskowski, the mayor of Warsaw, Poland, told ABC News Live on Thursday. “But we need assistance, we need international institutions in place. We need a relocation system in Europe and in the world, because we can’t do it alone.”

More than 3 million refugees have fled Ukraine, with over half moving to Poland, according to the United Nations. Warsaw, the capital of Poland, has seen a 20% increase in its population in just a few weeks, according to Trzaskowski. He said the city has welcomed over 300,000 Ukrainians but are no longer able to improvise.

Trzaskowski is calling on the European Union and the United Nations to help set up a system, which would help move refugees in Warsaw to other cities that are less overwhelmed and can better provide the physical and psychological care that’s needed.

“I’m calling myself in the middle of the night, my friends from different cities in Poland and in Europe, and I ask them for assistance. We bus people to different places all over,” Trzaskowski told ABC News Live. “We cannot do it anymore. We need a workable system.”

Trzaskowski said it’s not just beds and food that people need, but that as time goes on, new refugees are coming in having seen more destruction and are in need of immediate mental health services.

“At the beginning, three weeks ago, people who were coming to Warsaw were taken care of by their families and by their friends. Now, people come traumatized by war. They escape rockets, they escape bullets, members of families have been killed, members of their families are stranded in basements,” he explained. “They not only need shelter, they need reassurance. They need a helping hand.”

The mayor said Poland has tried to provide a sense of normalcy for families. Earlier this week, a bill was passed in Polish Parliament to provide Ukrainian children with free education and schooling. The mayor told ABC News Live that more than 10,000 Ukrainian students are already learning in Warsaw classrooms.

“We welcome them and we treat them like citizens,” Trzaskowski said. “We provide any help we can, but there is only so much that we can coordinate.”

Trzaskowski said Warsaw and all of Poland have tried their best to help during this crisis. Polish families have stood at the border, inviting refugees into their homes, feeding people who have gone days without eating or drinking water while traveling and making them feel welcomed into the country while the war continues.

“Without volunteers, without non-governmental organizations, we wouldn’t go anywhere,” the mayor said.

He emphasized that though these efforts have been able to provide for hundreds of thousands of Ukrainians, more still needs to be done. And without a plan going forward, they will not be able to continue this effort, he said.

The mayor went on to thank the United States for providing support and said it’s made a significant impact throughout this crisis.

“I want to thank President Biden and Vice President Kamala Harris, the whole Biden administration, and the U.S. Congress for being really tough on Russia, for imposing sanctions, for treating them seriously and for those words which are ringing in our ears, which say that the United States of America will defend every inch of NATO territory,” he told us. “And just because we can feel secure, all of us in Europe, because of that statement and because of the actions of the American government, we can do our job in a peaceful manner.”

Trzaskowski added that throughout this refugee crisis, he has looked to the bravery of leaders in Ukraine, which has given him courage to produce a plan that will give every refugee a place to call home while their nation is under attack.

“If President Zelenskyy in Kyiv is not panicking, we’re not going to either,” he said.

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(WASHINGTON) — Secretary of State Antony Blinken said Thursday that he personally believes war crimes have been committed in Ukraine, a day after President Joe Biden labeled Russian President Vladimir Putin a “war criminal” for the first time since Putin launched his invasion.

“Yesterday, President Biden said that in his opinion, war crimes have been committed in Ukraine. Personally, I agree,” Blinken said. “Intentionally targeting civilians is a war crime. After all the destruction of the past few weeks, I find it difficult to conclude that the Russians are doing otherwise.”

Before the U.S. officially labels Putin’s actions as war crimes, Blinken said State Department experts from the Office of Global Criminal Justice are documenting and evaluating evidence for a formal determination and will share those findings with those responsible for accountability. But he acknowledged reports on intentional attacks from the bombing of a Drama Theater housing children to opening fire at people waiting in line for bread.

“These incidents join a long list of attacks on civilian non-military locations across Ukraine, including apartment buildings, public squares, and last week, a maternity hospital in Mariupol,” he said. “I doubt that any of us who saw those images will ever forget.”

“There’s going to have to be, one way or another, accountability for this war of aggression,” he said of Putin.

But he warned of more darkness to come — Russia making renewed claims of genocide, using chemical or biological weapons and blaming Ukraine, sending its “mercenaries” to join the fight, and systematically kidnapping Ukrainian officials and replacing them with puppets — which he called a “terror tactic.”

While Ukrainian officials have been engaged in talks with Russian counterparts, Blinken expressed pessimism about those talks — saying they’ve not seen “any meaningful effort” by Russia to end the war through diplomacy. If anything, he warned, Putin indicated in his remarks Wednesday that he is doubling down.

Just moments before Blinken stepped out to speak, a State Department official confirmed to ABC News that a U.S. citizen was killed Thursday in Ukraine after Chernihiv regional police reported an American was killed by Russian shelling there. Two American journalists, a filmmaker and a Fox News cameraperson, were also killed this week covering the war.

As thousands flee the violence, Biden announced Wednesday the U.S. would provide Ukraine with $800 million in additional security assistance, bringing the total in aid over the past week to $1 billion. But Ukrainian President Volodymyr Zelenskyy’s central request — for a no-fly zone over Ukraine — has not been granted. However, he did offer an alternative before Congress on Wednesday: S-300s, a Soviet-era missile system that are well-suited to to defend against Russian attacks.

Following his request, NATO ally Slovakia said it’s “willing to” provide the replacements — as long as NATO fills the gap that providing its only air defense system will create in Slovakia.

“What would happen immediately when we decided to give it to Ukrainians is that we actually create a gap a security gap in NATO,” said Slovak Defense Minister Jaroslav Nad’ Thursday, at a joint press conference with Secretary of Defense Lloyd Austin in Bratislava. “Should there be a situation that we have a proper replacement or that we have a capability guaranteed for a certain period of time, then we will be willing to discuss the future of S-300 system.”

But it’s unclear if a guarantee has been made yet to Slovakia in order to get the systems to Ukraine. The three NATO countries that have S-300s are Slovakia, Bulgaria and Greece.

As the U.S. reaffirms it would not support a no-fly zone, despite Zelenskyy’s pleas, Austin also explained the decision and called on Putin to cease attacks on civilians in Ukraine.

“Enforcing a no-fly zone actually means that you’re in combat. You’re in a fight with Russia,” said Austin. “So, from a U.S. perspective, we’re, again, our position remains that we’re not going to do one,” he added.

Asked directly if Russia’s attacks against civilians in Ukraine constitute a war crime, Austin did not go as far as Biden and Blinken and said that the State Department is currently reviewing the reports of civilian attacks.

“If you attack civilians on purpose, target civilians purposely, then that’s not — that is a crime,” Austin said. “So, these actions are under review by our State Department, and, of course, there will be and there’s a process that will go through to review all of this.”

Amid concerns China could assist Russia with military equipment, Biden is scheduled to speak Friday with Chinese President Xi Jinping. He will also travel to Brussels next week in a show of unity to meet with NATO leaders.

Earlier in the day, Biden welcomed Irish Taoiseach Michael Martin for a virtual bilateral meeting in the Oval Office and said the leaders were “meeting in a moment when demands on unity in the world are really accelerating,” as Russia’s war in Ukraine continues.

“We have to be united and we certainly are,” Biden said. “But Putin’s brutality and what he’s doing, and his troops are doing in Ukraine is just inhumane.”

The Taoiseach echoed Biden’s view of Putin’s “unjustifiable and immoral war,” saying “I share with you our horror at the barbaric attack on the civilians,” and said Biden’s leadership through this has been “firm,” “determined,” and “strong.”

“Particularly your capacity to marshal like-minded democracies, the U.S., the European Union, the United Kingdom, the other — Canada and other like-minded democracies are coming together to respond in an unprecedented way to this barbaric attack on the women and children of Ukraine.”

ABC News’ Luis Martinez contributed to this report.

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