NY Times:

WASHINGTON, June 30 — American intelligence officials now believe that North Korea is developing the technology to make nuclear warheads small enough to fit atop the country's growing arsenal of missiles, potentially putting Tokyo and American troops based in Japan at risk, according to officials who have received the intelligence reports.

In the assessment — which they have shared with Japan, South Korea and other allies in recent weeks — officials at the Central Intelligence Agency said American satellites had identified an advanced nuclear testing site in an area called Youngdoktong. At the site, equipment has been set up to test conventional explosives that, when detonated, could compress a plutonium core and set off a compact nuclear explosion.

Some intelligence officials say they believe that the existence of the testing range is evidence that North Korea intends to manufacture much more sophisticated weapons that would be light enough to put onto its growing arsenal of medium- and long-range missiles.

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