Mr Putin knows that America's proposed anti-missile system would be too small to block Russia's still powerful missile armoury.
If a smaller device was indeed tested, analysts said this could take Pyongyang closer to building a warhead small enough to arm a missile.
North Korea claimed that a "miniaturised" device had been tested, increasing fears that Pyongyang had moved closer to building a warhead small enough to arm a missile.
Pyongyang claims its nuclear test involved a smaller and more powerful device - prompting concerns it could be moving closer to creating a warhead small enough to arm a missile.
The US and other regional allies fear North Korea is working to develop a nuclear warhead small enough to arm a missile, though it is not believed to have achieved this yet.
South Korea's military doesn't believe North Korea has a nuclear weapon small enough to mount on a missile, a defense ministry spokesman said Friday.
Shadows are now being armed with a small, still-classified guided missile.
It is thought to be the first time that the agency has acknowledged North Korea's capability to produce warheads small enough to fit onto a missile.
Regional neighbours and the US fear Pyongyang is working to build a nuclear warhead small enough to put on a missile, but believe it does not yet have the capabilities to do so.
North Korea has said its nuclear test in February involved a miniature device, a description U.S. and international experts said at the time could mean the government had developed a warhead small enough to mount onto a missile.
Although North Korea boasts of nuclear bombs and pre-emptive strikes, it is not thought to have mastered the ability to produce a warhead small enough to put on a missile capable of reaching the U.S. It is believed to have enough nuclear fuel, however, for several crude nuclear devices.
Tehran and Pyongyang have developed expansive military ties over the past three decades and have collaborated in developing missile systems, submarines and small arms.
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South Korea's Kospi shed 1.3% amid escalating fears over North Korea, which now appears to have developed a nuclear device small enough to mount on a ballistic missile.
It is seen as a key step toward its goal of building a bomb small enough to be fitted on a missile capable of striking the United States.
That test is seen as another step toward North Korea's goal of building a bomb small enough to be mounted on a missile that can hit the United States.
Observers fear North Korea is working towards creating a nuclear device small enough to fit on a long-range missile.
North Korea is believed to be working toward building an atomic bomb small enough to mount on a long-range missile.
North Korea is not believed to be capable of making a nuclear weapon small enough to fit on a long-range missile capable of hitting the United States.
If that missile were armed with even a relatively small and crude nuclear weapon and that warhead were detonated in space high over the United States, it would unleash large quantities of gamma rays.
Nor was it tied to the recent test of a medium-range missile, the No Dong, with which small nuclear weapons could be delivered against targets throughout South Korea and parts of Japan.
But a nuclear warhead would have to be small enough to fit onto, say, a Nodong missile - and it would have to be capable of withstanding the buffeting and other forces exerted on it during flight.
Or is she correctly discerning the migration of missile defense from a big issue to a compromisable small one?
He says North Korea is years away from developing a nuclear warhead that would be small, light and heat-resistant enough to launch on a missile.
The crater was extremely small, but eyewitnesses said they had seen both a plane and a missile.
Dr. Hamza revealed that Saddam now has a workable design for a small atomic weapon capable of being fitted aboard an extended-range Scud missile.
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Aegis began as a sea-based defense against hostile aircraft, but over three decades has evolved to become the most versatile missile-defense system in the world, due in no small part to the fact that destroyers and cruisers hosting the system can get wherever they need to be quickly.
They said Beijing was reluctant to take more than a few limited steps to show its displeasure with North Korea but was likely to respond to the U.S. missile-defense plans by upgrading plans to modernize China's relatively small nuclear arsenal.
And there will be thousands of small vendors flogging pink and orange neon cases for Apple iPhones, powered laptop backpacks, and USB missile launchers.
The most determined effort to develop a small, cheap guided weapon, though, is the Forward Firing Miniature Munition (F2M2, or Spike missile), from the Naval Air Weapons Station in China Lake, California.
Looking ahead, I can see more and more instances where I'll disagree with the president on very fundamental issues -- the issues of choice, the direction of the judiciary, tax and spending decisions, missile defense, energy and the environment, and a host of other issues, large and small.
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