Washington: US President Donald Trump on Wednesday brushed aside Ukraine's aspirations to join NATO, again repeating Russia's stance that the issue caused the three-year-old war.

"NATO -- you can forget about," Trump said when asked about a potential deal to end the war. "I think that's probably the reason the whole thing started."

The US president also opined that the European Union was born to "screw" the country, laying bare his hostility to the longtime US partner as he detailed new tariffs.

Trump's month back in the White House has been marked by soaring friction between Washington and its European allies, with the United States abruptly shifting gears on support for Ukraine and Germany's likely next leader urging Europe to seek to take greater control of its own defence.

"Look, let's be honest, the European Union was formed in order to screw the United States," Trump told reporters as he gathered his cabinet for the first time. "That's the purpose of it, and they've done a good job of it. But now I'm president," Trump said.

The European Commission shot back that the European Union is "the world's largest free market" and has been "a boon for the United States."

Former Swedish prime minister Carl Bildt, writing on X, said Trump had a "seriously distorted view of history" as the EU was "actually set up to prevent war on the European continent."

The United States for decades cheered on European integration, seeing the EU's formation in 1993 as a historic achievement to end conflict on a continent ravaged by two world wars.

Trump, by contrast, applauded Britain when it left the single European market and has vowed an "America First" policy of pursuing self-interest above any abstract concepts of partnership. Trump said at his cabinet meeting that the European Union has "really taken advantage of us."