Former Secretary of State Condoleeza Rice on Sunday praised President Joe Biden after NATO united under him in a way that it did not under President Donald Trump.

"There's this worry among generals whom I've talked with," Fox News host Harris Faulkner told Rice. "Nobody wants a world war. But that [Russian President Vladimir Putin] would do something at this point that he might not have done a few years ago in terms of more of a land grab, the Baltics for instance. And because of Article 5 with NATO, what does that mean for us. We get involved in war. We can't go to war with a nuclear power."

"We have to make sure that [Putin] really understands that the cost would be extraordinary to try to cross an Article 5 line," Rice replied. "An attack upon one is an attack upon all. And so the Baltic states are indeed protected under that guarantee by the United States of America."

"If it looks like he is not going to achieve his objectives, there is a chance that he pulls up," she continued. "But I want to make sure that he does."

"So what we're doing in reinforcing NATO forces in the Baltics and in Poland -- NATO's eastern flank, if you will -- this is the way to make sure that he knows the costs would be very high," the former secretary of state remarked.

Rice suggested that Biden has been able to "unite" NATO to push back against Putin's alleged war crimes to a degree that former presidents could not.

"It is certainly against every principle of international law and international order, and that's why throwing the book at them now in terms of economic sanctions and punishments is also a part of it," she said. "And I think the world is there. Certainly, NATO is there. He's managed to unite NATO in ways I didn't think I would ever see again after the end of the Cold War."

As president, Trump actively worked to undermine NATO and even considered withdrawing from the treaty organization.

UPDATE: Harris Faulkner was caught offguard by her answer.