In the event that Russia launches an attack or invasion against Estonia, the United States will enter the conflict, according to the head of the Department of the Defense.

Secretary of Defense Lloyd Austin III spoke Thursday at a meeting of NATO defense ministers in Brussels, Belgium. The conference focused heavily on the Russian invasion of Ukraine, which is approaching its year anniversary.

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Secretary of Defense Lloyd J. Austin III is seen leaving NATO headquarters at the end of the second of two days of defence ministers' meetings on Feb. 15, 2023, in Brussels, Belgium.

Secretary of Defense Lloyd J. Austin III is seen leaving NATO headquarters at the end of the second of two days of defence ministers' meetings on Feb. 15, 2023, in Brussels, Belgium. (Omar Havana/Getty Images)

Austin was asked by a reporter how the country could be confident they'd have the backing of U.S. military might in the event of a Russian invasion.

"You know, I'll just point to what our president, President Biden, has said a number of times and what I've also said. Our commitment to Article 5 is ironclad. And we take that very seriously and will live up to our commitments," Austin told the press.

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Secretary of Defense Llyod Austin participates in NATO defense ministers' meeting

Secretary of Defense Lloyd Austin (2ndL) and Estonia's Prime Minister Kaja Kallas (R, back) hold bilateral talks in Tallinn, Estonia, on Feb. 16, 2023.  (RAIGO PAJULA/AFP via Getty Images)

Article 5 of NATO’s Washington Treaty is known as "the principle of collective defence." It obliges all member countries to come to the aid of another member whose sovereignty or territorial integrity might be under threat.

NATO defines it as being "at the very heart of NATO’s founding treaty."

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Secretary of Defense Llyod Austin participates in NATO defense ministers' meeting

Secretary of Defense Lloyd J. Austin III holds a closing press conference during the second of two days of defense ministers' meetings at NATO headquarters on Feb. 15, 2023, in Brussels, Belgium. (Omar Havana/Getty Images)

The defense secretary explained that the US military has maintained a comprehensive presence within the Baltics since the beginning of the Russian invasion of Ukraine.

"We also set up, you know, back at Madrid, our president made the decision to rotate forces in and out of the Baltics on a consistent basis in a heel-to-toe fashion so that we had the, you know, consistent presence. We've lived up to that. We'll continue to live up to it," Austin said.

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Secretary of Defense Llyod Austin participates in NATO defense ministers' meeting

Secretary of Defense Lloyd Austin arrives for talks with Estonia's Prime Minister in Tallinn, Estonia, on Feb. 16, 2023. (RAIGO PAJULA/AFP via Getty Images)

Austin touted this level of military presence as a promise kept, stating that similar promises of military support would be kept if necessary.

"And the final thing I would just point out to you is that prior to Russia's invasion, you know, I met with your minister of defense and I told him that if Russia invaded Ukraine, we would deploy forces to Estonia the next day. And we did. We were the first to be here and we meant every word we said. And we'll live up to our commitments going forward. So we are committed to to Article 5. And you can bet on it."

Fox News' Stephanie Pagones contributed to this report.