NATO chief Mark Rutte and the new US ambassador sought to reassure European allies on Thursday that Washington will remain committed to the Western military alliance despite harsh words from US President Donald Trump.

NATO foreign ministers gathered in Brussels with Europeans hoping Secretary of State Marco Rubio will dispel doubts about the US stance, even with tensions rising over Trump's steep new trade tariffs.

As these tensions unfold, Rutte also highlighted a historic surge in European defence spending, the largest since the end of the Cold War, emphasising that while Europe is investing heavily in its own security, doubts about America's long-term commitment persist.

European belief in the US as the continent's ultimate protector against any attack from Russia has been severely shaken by Trump’s attempted rapprochement with Moscow and heavy pressure on Kiev as he seeks to end the war in Ukraine.

In addition, Washington has bluntly told European countries in recent months that it can no longer be primarily focused on the continent’s security and they will have to spend much more on defence.

The Trump administration's words and actions have raised questions about the future of NATO, the transatlantic bloc that has been the bedrock of European security for the past 75 years.

The US has no plans to immediately withdraw its military presence in Europe, despite its demands that European countries take care of their own defence, Rutte said ahead of the meeting of foreign ministers.

"There are no plans for them to all of a sudden draw down their presence here in Europe," Rutte said, referring to the US, before a meeting of NATO foreign ministers in Brussels.

"But we know that for America being the superpower they are, they have to attend to more theaters. It's really logical that you have that debate, and we are having that debate for many years."

Matthew Whitaker, who started as the United States' new permanent representative to NATO on Thursday, said he was starting in the job "at a critical moment in the history of the alliance".

"Under President Trump’s leadership, NATO will be stronger and more effective than ever before," he said in a statement.

"But NATO's vitality rests on every ally doing their fair share."

European ministers are also likely to use the meeting to try to influence the talks Trump has initiated with Russia over the war in Ukraine, which was triggered by Moscow’s 2022 invasion.

A senior NATO diplomat said there was unease among Europeans that they were not yet involved in negotiations that are key for Europe's security.

"That's hard to swallow, but that's a fact of life," said the diplomat, speaking on condition of anonymity.

Europe seeing 'biggest defence spending increase since Cold War'

Rutte also welcomed a historic surge in European defence spending and called for continued efforts to bolster military readiness amid rising global threats.

"We literally see hundreds of billions of euros rolling in," Secretary General Mark Rutte said at the start of a NATO foreign ministers' meeting in Brussels. "This is probably the biggest increase in defence spending here on the European side of NATO since the end of the Cold War. But we still need more."

He also said: "Let’s celebrate the fact that we have added, in aggregate, €700 billion ($770 billion) since 2017."

Welcoming efforts by the Trump administration to broker peace in Ukraine, the NATO chief said: "The Americans have broken a network. They are working with the Russians and Ukrainians to get to a peace deal … that should be enduring and lasting."

Rutte also highlighted Arctic security and stability in the Western Balkans as rising priorities.