Brussels, Belgium - The US is not planning to withdraw up to 40,000 troops in Europe, Washington's envoy to NATO said on Wednesday, denying recent reports.

NBC reported in mid-September that Washington was weighing cuts of 25,000 or more of its forces from Europe, citing anonymous US officials.

"Those reports are wrong," US ambassador to NATO Matthew Whitaker said during a defence conference organised by broadcaster Euronews.

"The plan hasn't even been finalized by the folks at the Secretary of War's policy shop," he added.

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The US administration launched a formal review of its military presence in Europe this summer, raising fears among allies that it could cut back its forces in European nations.

Whitaker said the US would "stay engaged in Europe".

The review is also looking at how US forces use military bases.

Washington has previously criticized European countries for not allowing the US to use NATO bases on their territory during the war against Iran.

"We're just doing a very kind of mathematical, mechanical analysis of how we're laid down globally because we have to address global challenges," Whitaker said.

Washington has already taken steps to change its presence in Europe, where it has around 80,000 troops. The US announced it would withdraw 5,000 troops from Germany in May.