美国有线新闻 CNN 朝鲜不断发射导弹挑衅 对美构成重大威胁（在线收听）

AZUZ: The U.S. director of national intelligence says because of its growing missile and nuclear capabilities, the Asian country of North Korea is increasingly becoming a grave national security threat to the U.S.

America has a few ways it could respond. It could launch a preemptive strike on North Korea, which carries a lot of risks. It can work with other countries to try to pressure North Korea to stop, which the U.S. is doing now. It can also refine and test its own defense technology, like a $40 billion missile defense system.

BRIAN TODD, CNN CORRESPONDENT: U.S. officials say it's like trying to hit a bullet with another bullet. The U.S. military attempted an exceptionally difficult missile interception, its first ever to shoot down a model of a long range intercontinental ballistic missile.

In a test taking place over the Pacific Ocean, a mock enemy ICBM fired from the Marshall Islands was targeted by an interceptor fired from an underground silo at Vandenberg Air Force Base north of Santa Barbara. U.S. officials say the interceptor hit its target, the stakes couldn't be higher.

How much pressure are they under to make this work?

KINGSTON REIF, ARMS CONTROL ASSOCIATION: So, this is a very crucial test for the Pentagon and for the Missile Defense Agency. North Korea is working on development of intercontinental ballistic missile that would be designed to target and hit the United States.

TODD: Adding to the pressure, the U.S. military's spotty track record in these tests. In a little over a decade, only about half the interceptors have hit their targets and three of the previous four tests failed.

Critics say the interceptors, based in California and Alaska were rushed into deployment and have had several mechanical problems.

REIF: Sometimes, the kill vehicle did not separate from the rest of the interceptor and at times, there have also been problems with the kill vehicle itself.

TODD: The interceptor test comes as Kim Jong-un crows about a missile his regime test-fired this week, which it claims has new in-flight guidance systems to make it more accurate.

VICTOR CHA, CENTER FOR STRATEGIC & INTL. STUDIES: North Korea is on the missile testing warpath right now.

TODD: A barrage of about a dozen missiles test-fired by Kim just this year and now, his regime in an announcement brags that Kim is preparing to send a, quote, bigger gift package to the Yankees.

Senator John McCain tells an Australian broadcaster he's not confident in America's missile defense systems to counter the North Korean threat.

SEN. JOHN MCCAIN (R), ARIZONA: I don't think that it's acceptable for the United States of America to have an intercontinental ballistic missile or a missile aimed at Australia with a nuclear weapon on it and depend on our ability to counter it with an anti-missile capability.

TODD: A key question now: what are the alternatives to this flawed missile interceptors?

CHA: In addition to missile defense, you have so-called left-of-launch cyber capabilities that are designed to hack North Korea's rocket systems.

You also have preemption, the possibility of a preemptive attack on North Korean missile launch pads or on their missiles themselves.

TODD: Analysts say that is the most risky option, that it could provoke Kim Jong-un to turn his guns on Seoul, or on the roughly 28,000 American troops in South Korea. Experts say the U.S. might launch a preemptive military strike on North Korea only if it became convinced that Kim Jong-un was about to fire a missile as an act of war and not just test one.

Brian Todd, CNN, Washington.