Pete Hegseth says the review would last for up to six months and include consultations with Congress which has legislated a minimum number of US forces in Europe.

The United States Defense Secretary Pete Hegseth has announced a new review of troop deployments in Europe, threatening to withhold some US dues to NATO if “free riding” allies did not meet their defence spending commitments.

Addressing defence ministers at NATO headquarters in Brussels on Thursday, Hegseth said the review would last for up to six months and include consultations with Congress, which has legislated a minimum number of US forces in Europe.

Hegseth’s remarks came a few weeks after the US told allies that if one of them comes under attack it would no longer supply certain warships and aircraft. European allies and Canada are trying to work out how to plug the gaps.

“Make no mistake about it, this will be a real review. It will be designed to ensure that NATO is moving fast and irreversibly towards Europe leading, stepping up to take primary responsibility for the defence of Europe,” Hegseth said.

He also slammed allies who did not support the US during its war with Iran, after some denied the US basing and overflight rights for war-related activities. He said the US review would ensure US basing and overflight rights were assured.

The US told allies last month that it had decided to shrink the pool of US military capabilities available to the alliance in a crisis.

That is meant to gradually end an “unhealthy codependence” on US forces as Washington faces the potential of simultaneous conflicts in multiple theatres, according to NATO’s top commander, US Air Force General Alexus Grynkewich.

Arriving for the NATO meeting, Hegseth said the US would be candid in public and private about countries that need to do more to meet their commitments.

“NATO 3.0 is post-Cold War recognition that it needs to go back to a real hardline military alliance that has real military capabilities capable of deterring right here on the continent and taking the lead for the conventional defence of Europe,” he said.

The comments come after European allies and Canada have launched an unprecedented effort to boost defence spending and expand their armed forces.

NATO Secretary-General Mark Rutte noted on Thursday that they spent $90 billion more on defence last year, a 20 percent increase compared with 2024.

Rutte also acknowledged that the reduction of US contributions to NATO’s crisis forces has already taken effect.

“The question yesterday came up: Is this immediate or not? It is immediate,” he told reporters.

Some ministers spelled out offers to raise their contributions to NATO’s crisis pool as they entered the Brussels meeting.

The US has not publicly disclosed details of its reductions, but they range from refuelling aircraft to fighter jets, drones and ships, according to figures provided to the Reuters news agency by a military source.