Key GAO findings:

— The current U.S. missile defense effort, under way for a decade at a cost of $80 billion so far, has not conducted flight tests independently certified as representing real-world conditions.

— The deployment of interceptors was "rushed", first by the second Bush administration in 2004, and is being rushed again by the Obama administration to meet a deadline for working European missile defense by 2018.

— A key radar for the planned European missile defense will interfere with broadband communications wherever it is deployed, a circumstance likely to provoke trouble in Romania and Poland.

— Over the GAO's opposition, the Pentagon has decided to proceed with simultaneous development and continued production of new interceptors, costing around $400 million, which failed in tests last year.