Dutch Prime Minister Mark Rutte, who will be NATO's next secretary-general, was criticised by other European Union leaders at a summit for his opposition to joint EU funding of defence projects, Poland's prime minister said on Friday.

Defence was high on the agenda at a European Union summit in Brussels that started on Thursday, with war raging in Ukraine and President Volodymyr Zelenskiy in attendance.

Leaders discussed proposals for common financing of defence projects in the bloc, but these faced opposition from Rutte and German Chancellor Olaf Scholz.

Rutte was confirmed on Wednesday as the next head of NATO and will take over on Oct. 1 from Jens Stoltenberg of Norway, who is stepping down after a decade in the post. Rutte has been a staunch defender of Ukraine in its war with Russia.

"Everybody, almost everybody, loudly reminded Mark Rutte that he will soon take up the role of NATO secretary general, and that he should be doing everything to make sure that Europe doesn't save money and resources (on defence)," Donald Tusk told reporters.

"He is a strong personality, an experienced politician, but I saw a blush on his face after everyone pointed out to him: 'Wait a minute, man, you should be mobilising everyone to spend more, not less, on defence."
Rutte told reporters following the summit that discussions on defence funding had been "tough".

"Clearly some countries were objecting to this idea, which was not officially on the table, but which was very much in the room, about eurobonds being used for defence expenditure," he said. "The Germans, we, I was very against it but we came to joint conclusions."

The Netherlands has long advocated fiscal discipline in the 27-nation bloc and is opposed to issuing joint debt.

Scholz said after the summit that the European Union should not be involved in financing armaments purchases or national defence budgets, but should focus its efforts on fostering better defence industrial coordination.

Tusk said he had been "very angry" at the arguments he had heard against common funding of defence projects.

Poland is spending around 4% of gross domestic product (GDP) on defence this year, the highest percentage in NATO.

Poland, Lithuania, Latvia and Estonia called on Wednesday for the European Union to build a defence line along the bloc's border with Russia and Belarus to protect the EU from military threats and other harmful activities from Moscow.