"I can assure you that the allies are united and stand together as one," Andrzej Duda told reporters after the online meeting, on the fifth day of fighting in Ukraine.
"Everyone realizes that we can only deal with this situation if we stand together," he said. "We must stand with Ukraine. We cannot accept attempts to change the world order by force."
Duda added that the West "will not give in to blackmail" and "will not be intimidated" by Russia, Poland's PAP news agency reported.
'We must do everything possible to end this war'
"It is impossible to tolerate the fact that children are being killed, that residential areas are being bombed, that people are being murdered," the Polish president said.
"We must do everything possible to end this war," he added.
Duda thanked Poles for "opening their hearts to Ukrainian refugees, for taking people into their homes, for offering gifts, for their extraordinary dedication to the Ukrainian people."
"I would like to thank my compatriots for this," he said.
'Bravery of the Ukrainian people': White House
Meanwhile, the White House said in a statement that Biden on Monday hosted a secure conference call "with Allies and partners about our unified response to Russia’s unjustified and unprovoked war on Ukraine."
It added that the leaders "recognized the bravery of the Ukrainian people in the face of Russian aggression and discussed their continued support to Ukraine, including security, economic, and humanitarian assistance."
They also discussed "their coordinated efforts to impose severe costs and consequences to hold Russia accountable while working to maintain global economic stability, including with regard to energy prices," according to the statement.
The White House also said that participants in the call included Canadian Prime Minister Justin Trudeau, European Commission President Ursula von der Leyen, European Council President Charles Michel, French President Emmanuel Macron, German Chancellor Olaf Scholz, Italian Prime Minister Mario Draghi, Japanese Prime Minister Fumio Kishida, NATO Secretary-General Jens Stoltenberg, Romanian President Klaus Iohannis, and British Prime Minister Boris Johnson, in addition to Poland's Duda.
Biden told reporters at the White House on Monday that Americans should not be worried about nuclear war, the Reuters news agency reported.
A day earlier, Russian President Vladimir Putin put his country's nuclear deterrent on high alert amid Moscow's ongoing invasion of Ukraine.
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Source: PAP, whitehouse.gov, Reuters