Defense Secretary Lloyd Austin on Friday warned that NATO will be drawn into war with Russia if Ukraine loses to Moscow.

"We know that if [Russian President Vladimir] Putin is successful here, he will not stop. He will continue to take more aggressive action in the region. And other leaders around the world — other autocrats — will look at this, and they'll be encouraged by the fact that this happened and we failed to support a democracy," Austin said Friday during a Republican-led House Armed Services Committee.

He also suggested that Lithuania, Estonia, and Latvia were especially vulnerable to invasion should Putin win the war in Ukraine.

"If you're a Baltic state, you're really worried about whether or not you're next," he said. "They know Putin. They know what he's capable of ... and, quite frankly, if Ukraine falls, I really believe that NATO will be in a fight with Russia."

Austin also urged continued support for Ukraine, saying Congress' failure to secure more funding for Kyiv sent an unfavorable signal to the world.

"Our allies are troubled by the message that we're sending," Austin said. "Certainly, it has impacted the morale of the Ukrainian troops. If we continue down this path, it will be a gift to Putin; and we certainly don't want that to happen."

"As others look at this, they will question whether or not we are a dependable ally or dependable partner," he added. "And that's very troubling for us as well."

Putin on Thursday warned NATO with a nuclear strike if it sends troops to Ukraine, saying during a speech to Russia's parliament that "consequences for the interventionists will be much more tragic."

"We, too, have weapons that can hit targets on their territory. This really threatens a conflict with nuclear weapons and, thus, the destruction of civilization," he added.

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