"Whoever wins those elections, we will work with Kamala Harris, we will work with Donald Trump, and make sure that the alliance stays united," Rutte said alongside German Chancellor Olaf Scholz.

Rutte said he had "no doubt" that whoever wins the election would continue to support NATO because it is "in the interest of the United States".

Western allies fear turbulent times ahead for the defence alliance formed at the start of the Cold War if Trump wins Tuesday's knife-edge election.

The alliance took a hit under Trump's 2017-2021 presidency as he berated allies for what he said was insufficient spending.

Trump warned in February he would encourage the Russians to do "whatever the hell they want" to NATO allies that do not pay more on joint defence.

Harris meanwhile has frequently pointed to Trump's remarks as she promises, like President Joe Biden, to work with allies and stand by NATO.

Western allies also fear a Trump presidency could mean a reduction in military aid for Ukraine from the US, which has driven NATO-wide support for Kyiv and been its biggest backer.

Rutte said reports of North Korean troops in Russia meant it was important to do "everything we can to keep not only the Euro-Atlantic but also the Indo-Pacific safe".

"This motivates us to step up to do even more," he said, labelling support by Pyongyang a "very serious development and an escalation".

Ukrainian President Volodymyr Zelensky made a request to join NATO when he recently presented his "Victory Plan" to Western allies.

Rutte said bilateral security agreements signed between several countries and Ukraine were "a bridge to NATO membership in the longer term".

"I'm absolutely convinced that one day Ukraine will be a member of NATO," he said.