Europeans fill most gaps left by US in NATO defence plans: Top commander

European NATO allies have largely filled the gaps left by the United States in the alliance's defence plans, NATO's top commander said on Thursday, adding the bloc was looking at workarounds to address the remaining shortfalls in a few areas.

"In a matter of weeks, European allies have largely filled the gaps left by US reductions to the NATO Force Model," NATO's top commander, US Air Force General Alexus Grynkewich, said in information provided to Reuters when asked for comment on the topic.

"And in those few areas where they haven't, where they do not currently have a like capability to replace, we are looking at alternate capabilities with matching effect."

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

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 Grynkewich.

In mid-June, NATO Secretary General Mark Rutte said other allies were increasing their contributions and would fill "a lot" of the gaps but did not give any details.

Citing a NATO source, Reuters reported on Wednesday that NATO would announce at next week's Ankara summit that its European members have filled almost all the gaps left by the United States in the alliance's defence plans.

The main gap NATO is still struggling to plug is in strategic bombers, where the US has said it will make only one aircraft available instead of two, said the source, speaking on condition of anonymity.

Cuts from fighter jets to drones

The US did not publicly disclose 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.

The number of KC-135 and KC-46 refuelling aircraft falls to 63 from 79, while only one strategic bomber and aircraft carrier would be allocated, rather than two.

The number of maritime patrol aircraft goes down to 15 from 26, the number of destroyers falls to nine from 17, and the only submarine carrying cruise missiles is also cut from the commitments.

The NATO alliance is under unprecedented strain, with some European countries concerned that Washington may fulfil repeated threats by US President Donald Trump to withdraw.