The sit-down in Florida is likely to further upset Budapest's allies after Orban drew widespread ire from European counterparts for meeting Russian President Vladimir Putin.

Right-wing Orban -- whose country took over the rotating presidency of the European Union this month -- has been a vocal supporter of Trump, and last met the Republican at his Mar-a-Lago residence in March.

Orban sparked uproar in the EU by jetting to Moscow last week to hold talks with Putin on what the Hungarian leader described as a "peace mission" over the war in Ukraine.

His Russia visit followed a trip to Kyiv for talks with Ukraine's President Volodymyr Zelensky.

The 27-nation EU bloc has condemned Russia's invasion of Ukraine and imposed unprecedented sanctions on Moscow.

"Viktor Orban has no mandate from the alliance, nor from the European Union, to conduct any form of negotiations," Finnish President Alexander Stubb said at the NATO summit.

"He can do it on his own behalf. But I fundamentally disagree about doing that. I simply do not see the purpose."

Orban, like Trump, has expressed skepticism about the role NATO countries are playing in support of Ukraine, and refuses to send Kyiv weapons saying it would fuel the conflict.

His meeting with Trump, who has been critical of the central role played by the United States in NATO, will come after US President Joe Biden has sought to rally the alliance at the Washington summit.

Biden has been seeking to reassure NATO counterparts -- and US voters -- about his leadership and fitness for office in the wake of a disastrous performance against Trump in a televised debate last month.