BRUSSELS (Reuters) – Kaja Kallas, the European Union’s next foreign policy chief, warned on Tuesday against making assumptions about what U.S. President-elect Donald Trump would do in Ukraine and warned that isolationism would never It had worked for the United States.

After a lawmaker said Trump could end US military support for kyiv and quoted Vice President-elect JD Vance as saying parts of Ukraine could remain with Russia as part of a peace deal, Kallas issued an oblique warning about isolationism.

“If we look at history, then isolationism has never worked well for the United States,” Kallas said.

Like many European leaders in recent days, he also sought to defend continued US support for Ukraine by linking the war to Trump’s concerns about the rise of China.

He said Russia would not be able to pursue the war as vigorously without Chinese support.

“If the United States is worried about China, it should worry about Russia first,” Kallas said.

Trump, who takes office in January, has repeatedly criticized the magnitude of U.S. aid to Ukraine and has said he will end the war quickly.

Kallas, who will succeed Josep Borrell in the coming weeks as EU foreign policy chief, said Europe needed to emphasize the links between Russia, Iran, North Korea and China when talking to its allies.

Kallas, a long-time strong supporter of Ukraine, also said there would be consequences elsewhere in the world if Russia is seen as having benefited from its invasion of Ukraine.

“If aggression bears fruit somewhere, it serves as an invitation to use it elsewhere; that is our concern,” he said.

The Russian invasion and uncertainty about the future of American support for Europe’s security have also put pressure on the continent’s leaders to do more on defense. Kallas emphasized that she was a strong supporter of those efforts.

“It is clear that we have to do more: produce more defense capabilities and ammunition,” Kallas said.

However, he said NATO must continue to play a leading role when it comes to European defence, with support from the EU on issues such as increasing weapons production.

“I don’t think (the) European Union needs separate military powers,” Kallas said.

He said he sees “synergy” between NATO and the EU “for NATO to prepare the military plans while (the) European Union and the member states really focus on how these munitions and capabilities are met.”

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Andrew Gray is Reuters European Affairs Editor. Based in Brussels, he covers NATO and the European Union and leads a pan-European team of reporters focused on diplomacy, defense and security. A journalist for almost 30 years, he previously worked in the United Kingdom, Germany, Geneva, the Balkans, West Africa and Washington, where he reported from the Pentagon. He covered the Iraq war in 2003 and contributed a chapter to a Reuters book on the conflict. He also worked at Politico Europe as a senior editor and podcast host, served as senior editor for a fellowship program for Balkan journalists, and contributed to the BBC’s From Our Own Correspondent radio programme.