European nations have expressed concerns about United States President Donald Trump's newly created Board of Peace, with European Council President Antonio Costa saying national leaders are especially worried about the scope of the new organization, which many critics say looks to be aimed at supplanting functions of the United Nations.

After a European Union leaders' summit in Brussels, Belgium on the subject of transatlantic ties, Costa said many European national leaders have issues with the fact that the constitution for the new organization has named Trump as its chairman for life, with several saying that would be undemocratic.

Others were concerned that the new organization was first mentioned as a temporary entity aimed at helping end the two-year Gaza conflict and oversee Gaza's reconstruction, but that it now seems to have morphed into an entity that is permanent and that gives Trump control over functions currently carried out by the UN, such as conflict resolution.

"We have serious doubts about a number of elements in the charter of the Board of Peace, related to its scope, its governance, and its compatibility with the UN Charter," Costa said, while adding that the EU stands "ready to work together with the US on the implementation of the comprehensive Peace Plan for Gaza, with a Board of Peace carrying out its mission as a transitional administration".

Spain's Prime Minister Pedro Sanchez said after the leaders' summit that his country had "declined" an invitation to join the new organization. So far, permanent members of the UN Security Council other than the US have not committed to participate in the new body.

But the US claims 35 of the 60 nations it has invited to join the Board of Peace have committed to take part.

The UK has said the reason it is reluctant to take part is the possible participation of Russia's President Vladimir Putin. France said it is disinclined to join because participation in the new organization would be incompatible with involvement in the UN. Norway and Sweden have also said they will not participate. Several other countries are weighing their options.

Euronews said Greece's Prime Minister Kyriakos Mitsotakis predicted most European countries will ultimately refuse to join the Board of Peace because of their concerns about the way it could supplant the UN.

"The consensus is that what has been announced by Donald Trump goes way beyond UN Security Council mandate," Mitsotakis said on Saturday. "I think we have to recognize that, moving forward, what has been established is something in which most European countries can't join."