Some members of Congress are rightfully calling for reform to the U.S. national missile defense program, but the change they suggest – removing the word “limited” from current U.S. policy – will carelessly expand the program and waste billions of dollars. If we’re serious about improving national missile defense, Congress must reform the objectives of the Missile Defense Agency to promote innovation and require a strict policy of “fly before you buy.”

For the past two decades, under both Democratic and Republican presidents, U.S. national missile defense policy has focused on intercepting a “limited” nuclear attack from North Korea, Iran, or another rogue actor. The Ground Based Midcourse Defense (GMD) program to do this has already cost $40 billion and counting, and its record has been far from exemplary: Only nine of 17 highly scripted tests have been successful since 1999, including three misses in the four most recent attempts, showing that the system is still undependable. As it stands, the President of the United States cannot rely on the program.

The lawmakers claim that this word “limited” has been the obstacle to success. It hasn’t. The truth is that “limited” national missile defense has been a necessary recognition of the intractable scientific and technical obstacles still preventing the GMD system from working.

To produce better results, policymakers need to reform the objectives of the Missile Defense Agency, the section of the Department of Defense responsible for GMD. That means promoting innovation, such as further research and development, instead of buying more ineffective hardware. That also means requiring the production of interceptors only after they have been successfully tested under realistic operational conditions, a logical policy the agency has often avoided to meet arbitrary deadlines – only to then miss the deadlines anyway.

It all began on March 23, 1983, when President Reagan proposed a nationwide ballistic missile defense apparatus, including the use of Space-Based Interceptors, to render “nuclear weapons impotent and obsolete.” The full initiative never came to fruition and, as someone who worked on the program, it was for good reason – the technical challenges were daunting and the potential financial burden was astronomical.

Then-Secretary of Defense Robert Gates, when asked whether expanding national missile defense was a sound proposition, replied that the new system “would be enormously destabilizing, not to mention unbelievably expensive.” If we were to expand our defensive capabilities, then Russia and China would feel justified expanding their offensive systems to overwhelm our missile defenses, leading the U.S. to build more offensive missiles, and so on. By “enormously destabilizing,” Secretary Gates understood a new nuclear arms race would jeopardize American national security. And he wasn’t kidding about the financial implications – a 2003 study estimated the lifetime cost of a layered nationwide missile defense system at as much as $1.5 trillion, when adjusted for inflation.

Other senior defense figures are worried that the current program is siphoning precious funds from proven and reliable conventional forces. In 2014, the-then Chief of Naval Operations, Admiral Jonathan Greenert, and then-Army Chief of Staff, General Raymond Odierno, jointly signed a memo calling the current national missile defense strategy “unsustainable” and proposing a full reassessment. Adm. Bill Gortney, former commander of the North American Aerospace Defense Command, has also criticized the program, simply saying: “It will not work.”

Unless the Missile Defense Agency shifts its focus to solving technical limitations, removing the word “limited” from U.S. policy will only result in massive new expenditures for unreliable hardware that is unlikely to make America safer.

Philip Coyle is the senior science fellow at the nonpartisan Center for Arms Control and Non-Proliferation. He served as director of Operational Test and Evaluation at the Pentagon from 1994 to 2001,