Secretary of Defense Ashton Carter leaves the podium after speaking at the NASA Ames Research Center in Mountain View, California, Aug. 28, 2015. The United States needs to enhance its half-century old radar system to effectively intercept Russian ballistic missiles, Carter said Tuesday. Reuters

U.S. radars in the Arctic are too old to effectively intercept Russian ballistic missiles, Defense Secretary Ashton Carter said during a panel discussion with troops Tuesday. Carter said the half-century old radar system in Greenland, a few hundred miles from the North Pole, needs to be modernized to work as an adequate early warning system against potential attacks, reported Russian media outlets.

“Russians have long-range nuclear-armed ballistic missiles,” Carter said. “We have to upgrade those radars … to cue missile defenses so that our missile defense interceptors can intercept them in flight.” He continued: "That [the Arctic base] is one of the places that ballistic missiles would overfly if they were en route to the United States. We have to … make them more sensitive so that they are able to detect threats earlier.”

The Thule Air Base in far northern Greenland was established as a staging area for operations against the Soviet Union during the Cold War. It once had 10,000 personnel from the U.S. and Denmark, which rules Greenland, but now houses about 1,000 workers.

Carter also said the U.S. needs modern radar systems to defend against possible missile attacks from China and North Korea. He said the U.S. will continue to be assert its rights under international law and its commitments to the North Atlantic Treaty Organization.

"We do not seek to make Russia an enemy," Carter said, "but make no mistake, while Vladimir Putin might be intent on turning the clock back for Russia, he will not turn the clock back for Europe."

Carter's remarks came during a speech to the American Legion on his "Force of the Future" plan to overhaul the military. Carter also praised a deal brokered by the United States and other countries aimed at deterring Iran from developing nuclear weapons. He said the deal being reviewed by Congress would not stop the United States from acting if Iran failed to meet its obligations.

"The deal places no limits whatsoever on our military," he said. "Our military option is real and will remain real."