Nawrocki attended the signing ceremony for the new international body but did not sign its founding charter, Polish media reported.
The initiative was initially presented as part of Trump’s plan to end the war in Gaza but is now widely seen as having a broader global role, prompting concern in Europe and elsewhere that it could rival or undermine the United Nations, news agencies reported.
Speaking at Thursday's ceremony, Trump said the Board would work with the UN.
"This is a very exciting day, long in the making," Trump said. "We’ll work with many others, including the United Nations."
He also referred to Gaza as a "beautiful piece of property" while discussing reconstruction of the war-ravaged territory, US broadcaster CNN reported.
'The biggest people, the most important people in the world'
Trump praised the members of his Board of Peace as "stars," saying they included "the biggest people, the most important people in the world."
"When you use that genius that you have—that very unusual, very inspired genius—when you use that for peace, the opposite of peace has no chance," he said.
US Secretary of State Marco Rubio said the initiative was designed to move beyond symbolism.
"This is not just a Board of Peace. This is a board of action," Rubio said. "It is going to be a successful effort, and you see it reflected here today among countries of different backgrounds from different parts of the world."
Trump, who will chair the board, has invited dozens of world leaders to join, including Poland's Nawrocki, and has said the body will address global challenges beyond Gaza.
Permanent membership requires a contribution of USD 1 billion to help fund the initiative, according to media reports.
Some traditional US allies have been cautious or have declined to join. France has rejected the proposal, Britain said on Thursday it would not participate for now, and China has yet to state whether it will join, the Reuters news agency reported.
Nawrocki said on Wednesday that Poland views participation in the initiative as important but that any international agreement must fully comply with Poland’s constitution and legal procedures.
His top foreign policy aide, Marcin Przydacz, said on Thursday that Poland needs more time, information and legal analysis before deciding whether to join.
Russia said late on Wednesday that it was studying the proposal after Trump said Moscow would take part, according to Reuters.
Hungarian Prime Minister Viktor Orban, a close Trump ally, was among those signing the Board of Peace charter in Davos on Thursday.
The Board’s formation was endorsed by a United Nations Security Council resolution as part of Trump’s Gaza peace plan, but UN spokesman Rolando Gómez said on Thursday that any UN engagement with the board would be limited to that framework, Reuters reported.
It said about 35 countries have committed to join, including Saudi Arabia, the United Arab Emirates, Egypt, Turkey and Belarus.
Critics said few of the countries that have embraced the initiative are democracies.
The ceremony took place in Davos during the annual World Economic Forum, which brings together global political and business leaders.
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Source: CNN, IAR, PAP, Reuters, TVN24
Click on the audio player above for a report by Agnieszka Łaszczuk.