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.

"Most may not know – although there was some reporting overnight about this – that in a matter of weeks, European allies have largely filled the gaps left by U.S. reductions to the NATO Force Model," NATO's top commander, U.S. 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."

Citing a NATO source, Reuters reported on Wednesday that NATO will 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.