British defence sources are at pains to point out that the NATO force's only purpose is to collect weapons surrendered voluntarily.

CNN: How arms will be 'harvested'

"The United States should be able to clearly state that the only purpose we hold nuclear weapons for is to deter the use of nuclear weapons, " said Daryl Kimball, executive director of the Arms Control Association.

WSJ: U.S. Keeps First-Strike Nuclear Strategy

The main purpose for a testing phase of any new weapons system is to iron out bugs -- it is supposed to find opportunities for product improvement.

CENTERFORSECURITYPOLICY: Center For Security Policy

Now, administrations in the United States and Britain are fending off accusations that they misled the public -- either unintentionally or on purpose -- about the existence of these weapons.

CNN: War of words over Iraqi weapons

Some of these knives are primarily weapons and do not serve the similar purpose as what you would call a small pocketknife.

CNN: March 7, 2013 -- Updated 0312 GMT (1112 HKT)