United States Defence Secretary Pete Hegseth announced a new review of America’s troop deployments in Europe on Thursday and threatened to withhold some US dues to NATO if “free riding” ​allies did not meet their defence spending commitments.

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

While he did not explicitly say the review could result in reductions in US force deployments in Europe, he stressed the goal would be to prompt the continent to do more while ensuring the US military would be able to meet its global commitments.

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

Hegseth 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.

His comments came as countries in the alliance scrambled to fill gaps in their crisis forces — national capabilities committed to ​the transatlantic alliance in an emergency — after Washington cut some contributions with immediate effect.

The US told its allies last month that it had decided to shrink the pool of US military capabilities ​available to the alliance in a crisis, raising urgent questions as leaders prepare for a NATO summit in Ankara on July 7-8.

The move is meant to gradually end an “unhealthy co-dependence” 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 a meeting with his counterparts at NATO’s Brussels headquarters, Hegseth said the US would be candid in public and ​private about countries that need to do more to meet their commitments.

“[There are] some that still need to do more, and we will be candid about that, both in private and ​in public. I think that’s important, friends being honest with friends,” Hegseth said.

“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.”

‘It is immediate’

NATO chief Mark Rutte acknowledged that the reduction of U.S contributions to NATO’s crisis forces had already taken effect.

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

“However, why I’m a little bit reluctant to say this is because it is a planning tool. So what would happen in reality? If war would break out … all allies, including the US, will max out what they can do to make sure we can fight the war.”

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

Belgian Defence Minister Theo Francken said his country would contribute more to NATO’s crisis forces to help replace some US capabilities, including with F-16 fighter jets and MQ-9B SkyGuardian drones.

“There will be heavy discussions on who is doing what, but I can say that Belgium is contributing,” the ​minister said.

Plugging other gaps will take longer as Europeans lack weapons such as deep strike missiles, prompting German Defence Minister Boris Pistorius to ​call for a synchronised process ⁠to prevent “dangerous capability gaps in Europe”.

“It is difficult and dangerous for the security of NATO’s territory in Europe if capabilities are withdrawn very quickly without having clarity when they can be compensated for,” he warned, citing deep strike as one of the capabilities hard to replace.

“There, we will need either stop-gap solutions or time before their withdrawal. This will need to be negotiated with our American partners. Generally, we ⁠will be ​able to compensate much but we will need some more time,” Pistorius said.

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 Reuters by a military source.

The number of US F-15 and F-15E fighter jets available to NATO will fall by a third ​to 99 and the number of MQ-4 and MQ-9 Reaper drones by half to 12, according to the source.