"Our concern is a resurgent Russia and a very, very aggressive China," Carlisle said Sunday in an interview with USA Today newspaper, speaking about interceptions of US warplanes by Russian and Chinese aircraft.
He added that the concerns are caused by attempts of Moscow and Beijing to expand their influence in Eastern Europe and the Pacific region.
"Their intent is to get us not to be there… So that the influence in those international spaces is controlled only by them. My belief is that we cannot allow that to happen. We have to continue to operate legally in international airspace and international waterways," Carlisle added.
In late April, a Russian Su-27 fighter jet intercepted a US RC-135 performing aerial reconnaissance near the Baltic Sea. The Pentagon condemned the action as unprofessional, while the Russian Defense Ministry defended its pilots as operating in accordance with international regulations.
The Russian air intercept followed only weeks after two Russian Su-24 jets performed a training exercise in close proximity to US Navy destroyer Donald Cook in the Baltic Sea. Moscow later claimed the incident was legitimate and took place at a safe distance from the vessel.