WASHINGTON (Sputnik) — Cook said to the daily Defense Department press briefing that Washington "remains confident in our missile defense."
"We feel confident in our ability to protect the homeland… We feel confident in our ability to deter this threat and protect American citizens."
Cook acknowledged that the GBIs mainly deployed at Fort Greely in the US state of Alaska had not successfully intercepted any target intercontinental ballistic missiles (ICBMs) in any tests in more than two and a half years.
However, Cook noted the US missile defense system was a multi-layered one.
"There are layers in terms of our ballistic missile defense (BMD)… That comprehensive defensive system we feel very confident in… We are not relying on any one thing to protect the United States," he said.
The GBI program has been plagued with problems over the past 12 years. Around 30 GBIs are currently deployed and the Obama administration has made plans to increase that force to 44 by the end of 2017.