WASHINGTON

US Secretary of Defense Lloyd Austin on Wednesday vowed to continue to strengthen NATO's collective defense and deterrence against any challenge.

"As this (Biden) administration has made very clear, we will not be dragged into (Russian President Vladimir) Putin's reckless war of choice.

"But we will stand by Ukraine as it fights for its sovereignty and security. We will defend every inch of NATO," Austin said at the NATO Public Forum.

NATO leaders on Tuesday gathered in the US for a three-day summit to mark the military alliance's 75th anniversary.

"We have built the strongest and most successful defensive alliance in human history," Austin said, adding that without NATO, the past 75 years would have been "far different and far more dangerous."

Since the start of the Ukraine-Russia war in 2022, Austin said NATO's forward defense posture has been bolstered with more troops in high readiness, larger exercises, sharper vigilance, and multinational battle groups in eight countries.

"NATO is now larger than ever. And our new allies in Finland and Sweden have brought the alliance's membership to 32. And make no mistake. Putin's war is not the result of NATO enlargement. Putin's war is the cause of NATO enlargement," he added.