Most NATO members aren't on track to meet their defense spending commitments, which could leave the United States with little backup if an allied country were attacked, according to a national security adviser to former President Trump.

The allied countries pledged in 2014 to increase their military spending to 2% of their GDP by 2024 to comply with NATO's Article 5, which stipulates that an attack on any member is treated as an attack on all. But most NATO countries haven't met that goal, and some have slipped further away in recent years, according to defense expenditure data collected by the alliance.

"If you don't get to 2% GDP, you will not have the military structure, the military forces to be able to support the rest of the alliance as they enforce Article 5," retired Lt. Gen. Keith Kellogg previously told Fox News.

LT. GEN. KELLOGG: NATO’S ARTICLE 5 RELIES ON ALLIES FUNDING DEFENSE 

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While the combined average spent on defense has increased since 2015, only nine of the 30 NATO nations spent 2% of their GDP on defense last year, according to NATO estimates. In 2022, $1.190 trillion was the total amount spent on defense by the allies. Of that, $822 billion, or 69%, was spent by the United States, equaling 3.47% of its GDP. 

"The amount of money that we're putting into NATO is well over the 2% GDP," Kellogg said. "We clearly understand what Article 5 means. In fact, we would respond quite well to it."

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nato defense spending

Only 9 of the 30 NATO countries spent 2% of GDP on defense in 2022 as stipulated in Article 3.  (North Atlantic Treaty Organization )

Last month, President Biden spoke to a group of NATO leaders and reaffirmed the U.S.'s commitment to the military alliance

Putin "doubts our continued support of Ukraine. He doubts whether NATO can remain unified," Biden said in his speech from the Royal Castle in Warsaw. "But there should be no doubt, NATO will not be divided, and we will not tire."

"Article 5 is a sacred commitment the United States has made," Biden continued. "We will defend literally every inch of NATO."

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The United Kingdom contributed the second-largest dollar amount to its defense, spending 2.12% of its GDP, or $72 billion. The other countries that reached 2% were: Greece, Poland, Lithuania, Estonia, Latvia, Croatia and Slovak Republic, according to NATO estimates. 

"I think you can count on a handful of those nations that I guarantee you will be there in the middle of a fight," Kellogg said. "They're going to fight quite effectively." 

nato flag soldier

The United States contributed 69% of the total $1.190 trillion spent on defense by the allies in 2022.  (Laura Hasani/Reuters)

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But some nations' military spending declined. Canada, for example, spent 1.27% of its GDP on defense in 2022, down from 1.32% in 2021 and 1.42% in 2020, NATO estimates show. 

Spain, the second-lowest contributor in terms of GDP, decreased its military spending last year to 1.01% from 1.04%. 

France, Germany, Czech Republic, Hungary, Turkey, Norway, Slovenia, Portugal and Italy also decreased their percentage of military spending in 2022, moving further away from the 2% goal.

"They're going to hold America's coat," Kellogg said. "They’re like, 'you guys go fight it and we'll kind of be back here to support you.’"