European officials will also be seeking a strong common stance on Russia at the one-day gathering.

Rutte, who was Dutch prime minister during Trump's first 2017-2021 presidency, said that "I worked with him very well for four years. He is extremely clear about what he wants. He understands that you have to deal with each other to come to joint positions. And I think we can do that."

And he insisted that the common challenges posed by Russia in Ukraine affected both sides of the Atlantic.

"Russia is delivering the latest technology into North Korea in return for North Korean help with the war against Ukraine. And this is a threat not only to the European part of NATO, but also to the U.S. mainland," Rutte said coming into the summit.

Trump strongly pushed the European NATO allies to spend more on defense during his first presidency, to up and beyond 2% of gross domestic product and to be less reliant on U.S. military cover. That point has totally sunk in.

"When he was president, he was the one in NATO who stimulated us to move over the 2%. And now, also thanks to him, NATO, if you take out the numbers of the U.S., is above the 2%.," Rutte said.

Charles Michel, the council president of the 27-nation European Union, agreed that the continent needed to become less reliant on the United States.

"We have to be more masters of our destiny," he said. "Not because of Donald Trump or Kamala Harris, but because of our children."

During his election campaign, Trump has threatened anything from a trade war with Europe to a withdrawal of NATO commitments and a fundamental shift of support for Ukraine in its war with Russia -- all issues that could have groundbreaking consequences for nations across Europe.

Trump has said he would end the war in Ukraine, now well into its third year, within days of being reelected. Ukraine and many of its European backers fear that this means a peace on terms favorable to Russian President Vladimir Putin and involving the surrender of territory.

European allies in NATO hope to convince Trump that if he helps to negotiate any peace, it should be done from a position of strength, for both Ukraine and the United States.

Hungarian Prime Minister Viktor Orban, the summit's host and an ardent Trump fan, said early Thursday that he already had a phone call with the incoming president overnight, announcing that "We have big plans for the future!"

So did hard-right Italian Prime Minister Giorgia Meloni, who lauded the "deep and historic strategic partnership that has always tied Rome and Washington."

That partnership came under constant pressure during Trump's first term, from 2017-2021.

Trump's administration slapped tariffs on EU steel and aluminum in 2018, based on the claim that foreign products, even if produced by American allies, were a threat to U.S. national security. Europeans and other allies retaliated with duties on U.S.-made motorcycles, bourbon, peanut butter and jeans, among other items.

The impact of the U.S. election result could be felt in Europe for years to come, on issues including the wars in Ukraine and the Middle East, as well as migration and climate change.

Among the leaders, Zelenskyy, who is expected to make another plea for more aid as his country fends off Moscow's invasion. The timing is laden with significance as Trump has vowed to end the war "within 24 hours" of being elected -- something leaders in Kyiv interpret as an impending evaporation of U.S. support following Trump's win.

Further compounding an already complicated situation, Germany -- Europe's troubled economic juggernaut -- sank into political crisis after German Chancellor Olaf Scholz fired his finance minister. It raises the specter of an election in a few months and yet another standoff between the emboldened hard right and the establishment parties in Europe.

Those two combined "adds even more pepper and salt to this situation," Polish Prime Minister Donald Tusk said.

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Lorne Cook contributed to this report from Brussels.