UPDATED WASHINGTON: The United States must not hand over sensitive missile defense technology to Russia even if it means abandoning White House plans for a European missile shield, a key GOP lawmaker says.

There already have been numerous instances by Russia to obtain American military secrets even after the collapse of the Iron Curtain the early 1990s, according to Sen. Mark Kirk. Handing over classified U.S. missile technology to Russia will let them to achieve “through diplomacy what couldn’t be done through . . . espionage,” he said shortly after his speech at a national security symposium in Washington this week. Lack of access U.S. military know-how was one the main reasons Russian President Dimitri Medvedev recently broke off talks with the White House over its European missile defense plans.

The European Phased Adaptive Approach is a network of land and sea-based missiles designed to counter potential missile strikes launched by Iran. Cooperation with Russia is integral to making the system work. Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey last week said the U.S. was committed to finding “common ground” with Russia on the plan. He acknowledged that part of any agreement could include information sharing with Moscow. That kind of cooperation would hand Tehran exactly what they need to deter the European missile shield, courtesy of their friends in Moscow.

“I don’t think we should share classified information with Russia because I think it will be immediately shared with Iran,” according to Kirk. Emphasizing the point, Kirk claimed Tehran will likely hand over any intelligence gathered from the American spy drone captured by Iran earlier this week. “Let’s be clear eyed about who the Russians are and who they talk to. Regularly.” Kirk said. Russia, and possibly Iran, would have access to the ins and outs of American missile defense operations if a deal is struck with Moscow. That information can be used by Russia or Iran to counter the EPAA or any American missile defense program the U.S. decides to field. The Republican senator claims he’s not alone in his concern over Russian-Iranian ties. “Almost every member of Congress would understand that there is a significant possibility that any [missile] data given to Russia” will end up in the hands of the Iranians, he said.

Dempsey was clear that information exchanges between the U.S and Russia was not a foregone conclusion. The four-star general noted that several steps must still be taken before those exchanges will happen. But with EPAA talks currently stalled, its unclear what the White House and the Pentagon are willing to give up to bring Russia back to the negotiation table.