Washington (CNN) The outgoing Army chief of staff said Wednesday that Russia posed the "most dangerous" threat facing the United States today, thanks to its "sophisticated" operations in Ukraine.

Gen. Raymond Odierno, who is leaving his post, estimated that only a third of U.S. brigades are capable of operating at the level of the hybrid warfare Russia is undertaking there. And he worries that Russia could next intervene in NATO allies like Latvia or Estonia.

"They are more mature than some other of our potential adversaries, and I think they have some stated intents that concern me in terms of how the Cold War ended," Odierno said of Russia when asked by CNN. "They have shown some significant capability in Ukraine to do operations that are fairly sophisticated, and so, for me, I think we should pay a lot of attention."

Odierno explained that he's concerned that Russia underestimates the extent to which NATO partners would defend the Latvians and Estonians, a miscalculation that could lead to conflict. The solution, he argued, would be to increase response capabilities in order to deter any possible Russian aggression.

"We have deterrent there and I think we're doing a good job with that," he said. "What we have do in the next several years is continue to increase that so the risk goes up for anybody who might consider operations in Eastern Europe."