In Poland on Thursday, Vice President Kamala Harris reiterated the United States’ commitment to protecting its NATO allies against Russian aggression amid Vladimir Putin’s war on Ukraine while calling for an international war crimes investigation of the Kremlin. 

“I am here in Poland as an expression of the enduring and important relationship between the United States and Poland,” Harris said in a joint news conference with Polish President Andrzej Duda after their meeting. “That, again, has been longstanding, but in particular on the issue of Ukraine, is unified and is clear: We will do everything together in partnership, in solidarity to support what is necessary at this very moment in terms of the humanitarian and security needs of Ukraine and the Ukrainian people.”

The U.S. is not directly involved in the war in Ukraine, but has given more than $1.2 billion in security assistance to Ukraine since President Joe Biden took office last year. 

The U.S., however, has deployed thousands of troops to reinforce NATO’s eastern flank, including an additional 4,700 service members sent to Poland. Harris said the U.S. also has delivered two Patriot missile defense systems to Warsaw. 

“The United States’ commitment to Article 5 is ironclad,” Harris said. “The United States is prepared to defend every inch of NATO territory. The United States takes seriously that an attack against one is an attack against all. We are here today to restate that commitment.”

Harris commended Poland for taking in about 1.5 million Ukrainian refugees and announced that the U.S. is donating an additional $53 million to assist with humanitarian aid. 

“We will continue with the support that we can give you, Mr. President, in terms of the work that you and the people of Poland have been doing to bear this burden, but in a way that really has been with such grace and such generosity,” Harris said.

She also noted that the House of Representatives approved a funding bill that includes $13.6 billion in aid to help Ukraine, some of which would be distributed to other countries taking in refugees. The Senate must still approve the legislation before sending it to Biden’s desk.

“When we talk about humanitarian aid, it is because, yes, the assistance is necessary, but what compels us also is the moral outrage that all civilized nations feel when we look at what is happening to innocent men, women, children, grandmothers, grandfathers, who are fleeing everything they've known,” Harris said. “Our outrage, which compels not only our security assistance but our humanitarian assistance, is rooted in the fact that also we support the people of Ukraine who have shown extraordinary courage and skill in their willingness and, yes, ability to fight against Putin’s war and Russia's aggression.”

Duda called Harris’ visit to Warsaw “a very clear political message where the most important things are happening today.”

“We have to rescue Ukraine,” the Polish president said. “All of us are acutely aware of that. All hands should be on board. Ukraine needs to be helped, and we have to stay united in that respect.”

Citing Wednesday’s bombing that destroyed a children’s and maternity hospital in the port city of Mariupol, Ukraine, killing at least three people and wounding 17 others, Harris said Russia has committed “atrocities of unimaginable proportion.”

Asked if the U.S. would support an international investigation into whether Russia has committed war crimes, the vice president said “absolutely.”

“When it comes to crimes and violations of international norms and rules, we are also very clear than any intentional attack on innocent civilians is a violation,” said Harris, who stopped short of explicitly accusing Russia of war crimes.

“Pregnant women going for health care being injured by, I don't know, a missile, a bomb in an unprovoked, unjustified war where a powerful country is trying to take over another country, violate its sovereignty, its territorial integrity for the sake of, what, nothing that is justified or provoked — absolutely, there should be an investigation,” she said. “And we should all be watching, and I have no question the eyes of the world are on this war and what Russia has done in terms of this aggression and these atrocities.”

Duda said, “It is obvious to us that in Ukraine Russians are committing war crimes.”

The meeting between Harris and Duda came amid a public communication breakdown between the two countries over a Polish plan to supply MiG-29 planes to Ukraine. The U.S. had entertained the idea of replacing Poland’s planes with F-16s. 

The Polish government on Tuesday announced a plan to transfer its Russian-made fighter planes to a U.S. military base in Germany, with the expectation that the planes would then be handed over to Ukrainian pilots trying to fend off Russian forces. 

But the Poles didn't run that idea past the Biden administration before going public with it, and the Pentagon quickly dismissed the idea as not tenable.

On Wednesday, Gen. Tod D. Wolters, the top U.S. military commander in Europe, thanked Poland for its offer but said that sending the planes to Ukraine would be a “high-risk and low-gain” venture.

Wolters said the most effective way to support the Ukrainian military “is to provide increased amounts of anti-tank weapons and air defense systems.”

Wolters says Ukraine already has enough warplanes and that sending the planes “may be mistaken as escalatory and could result in Russian escalation with NATO … producing a high-risk scenario.”

Asked about the situation during Thursday’s news conference, Harris did not directly address it, but said, “The United States and Poland are united in what we have done and are prepared to do to help Ukraine and the people of Ukraine.”

Duda said Poland had offered to donate the planes to NATO for the alliance to determine how they might be used. He insisted Poland was not acting unilaterally, but as a “reliable member of NATO.” He added that Poland did not expect anything in return for the planes.

The Associated Press contributed to this report.