Just days after a Pentagon official revealed that Russia is building a submarine that would have the capability to launch nuclear weapons against vital U.S. targets, an U.S. Air Force general has stated on Monday that the Russian military has been beefing up its air forces, closing the gap in air power between the U.S. and Russia considerably.

General Frank Gorenc, commander of U.S. Air Forces in Europe, states that Russia has been on the move to upgrade its air power after the invasion of Georgia in 2008. Speaking at an annual Air Force Association Conference, Gorenc stated that he was concerned about Russia's moves to increase the quality and quantity of its aircraft, both manned and unmanned, according to Radio Free Europe.

"The alarming thing is that the Russians are catching up. They've closed the gap," he said. "The advantage that we had from the air, I can honestly say, is shrinking."

The general further said that apart from air power, Russia has also been strengthening its surface-to-air missile defense systems. Two advanced systems have already been set up around the Crimea region of Ukraine, which was annexed by Russia in 2014. Similar missile defense systems have also been set up in Kaliningrad, a Russian enclave between Poland and Lithuania, reports MSN News.

The U.S. has been on the lookout for aggressive moves and military development in China, which has been upgrading its military lately. However, Gorenc states that Russia must also be watched just as much, if not more carefully than China.