Only Hungary, whose leader is a close Trump ally, gave an unequivocal acceptance in response to the invitations, which have been addressed to some 60 nations and began arriving in European capitals on Saturday, according to diplomats.
Other governments appeared reluctant to make public statements, leaving officials to express concerns anonymously about the impact on the work of the UN.
The board would be chaired for life by Trump and would start by addressing the Gaza conflict and then be expanded to deal with other conflicts, according to a copy of the letter and draft charter seen by Reuters.
Member states would be limited to three-year terms unless they pay $US1 billion ($A1.5 billion) each to fund the board's activities and earn permanent membership, the letter states.
"This simply offers permanent membership to partner countries who demonstrate deep commitment to peace, security, and prosperity," the White House said in a post on X.
Italian Prime Minister Giorgia Meloni, visiting South Korea, told reporters her country was "ready to do our part", although it was not clear whether she was specifically referring to Gaza or the broader peace.
Canada's Prime Minister Mark Carney said on Sunday he had agreed to Trump's Board of Peace for Gaza in principle although details were still being worked out.
A mandate for a Board of Peace was authorised by the United Nations Security Council in November, but only through 2027 and solely focused on the Gaza conflict. Russia and China, two veto wielding powers, abstained, complaining that the resolution did not give the UN a clear role in the future of Gaza.
The inclusion of a 'charter' in the invitation letter stoked concerns among some European governments that it could undermine the work of the United Nations, which Trump has accused of not supporting his efforts to end conflicts around the world.
"It's a 'Trump United Nations' that ignores the fundamentals of the UN charter," said one diplomat.
Three other Western diplomats said it looked as if it would undermine the United Nations if it went ahead.
A further three diplomats and an Israeli source said that Trump wanted the Board of Peace to eventually have a broader role beyond Gaza that would oversee the other conflicts that Trump has said he has resolved.
The leaders of France, Germany, Italy, Hungary, Australia, Canada, the European Commission and key Middle East powers were among those invited, according to officials.
"We have, of course, accepted this honourable invitation," Hungarian Prime Minister Viktor Orban, a close ally of Trump, wrote on X.
The document said "durable peace requires pragmatic judgement, common-sense solutions, and the courage to depart from approaches and institutions that have too often failed". There was a "need for a more nimble and effective international peace-building body", it added.
A spokesperson for UN Secretary-General Antonio Guterres said Guterres "believes Member States are free to associate in different groups" in response to a question about the draft US charter for a Board of Peace.
"The United Nations will continue with its mandated work," deputy UN spokesperson Farhan Haq said.
Trump, who covets the Nobel Peace Prize, said in the letter that the board would convene in the near future, adding: "This board will be one of a kind, there has never been anything like it!"
