On Saturday, US President Joe Biden met with top Ukrainian government officials in Warsaw as part of his visit to Poland to show support for NATO’s eastern flank in the face of Russia’s invasion of Ukraine.

Biden attended a meeting with Ukraine’s Foreign Minister Dmytro Kuleba and Defense Minister Oleksii Reznikov, as well as Secretary of State Anthony Blinken and Defense Secretary Lloyd Austin.

Kuleba told reporters that Ukraine had received additional security pledges from the US on developing defense cooperation, while Reznikov expressed “cautious optimism” following the meeting with Biden.

“President Biden said what is happening in Ukraine will change the history of the twenty-first century, and we will work together to ensure that this change is in our favor, in Ukraine’s favor, in the favor of the democratic world,” Kuleba said shortly after.

Following a separate meeting with his Polish counterpart, Andrzej Duda, Biden called for “constant contact” between the US and Poland, and reaffirmed Washington’s “sacred” commitment to security guarantees within NATO, which Poland is a member of.

Ukraine is not a member of NATO, and the United States is wary of getting dragged into direct confrontation with Russia, but with the war at the borders of the defence alliance, Washington has pledged to defend every inch of NATO territory.

The White House said that in a speech in Warsaw later on Saturday Biden “will deliver remarks on the united efforts of the free world to support the people of Ukraine, hold Russia accountable for its brutal war, and defend a future that is rooted in democratic principles”.

Biden has held three days of meetings with allies in the G7, Europe and NATO, and visited with U.S. troops in Poland on Friday.

In Warsaw, he also visited a refugee reception centre at the national stadium. More than 2 million people have fled the war to Poland, out of the roughly 3.8 million who have left Ukraine all together.

Standing outside, Hanna Kharkovetz, a 27-year-old from the northern Ukrainian city of Kharkiv, expressed frustation the world was not doing enough to help.

“I don’t know what he wants to ask us here. If Biden went to Kyiv … that would be better than speaking here with me,” she said as she waited to register her mother for a Polish national ID number.