President Bush has warned North Korea against testing a long-range missile as tension continues to mount over Pyongyang's intentions. U.S. officials are considering activating an unproven missile defense system. Leta Hong Fincher has more on whether a U.S. missile interception would work.

President Bush

President Bush said Wednesday he expects North Korea to abide by international agreements it has made on missile tests. "We think it'd be in the world's interest to know what they're testing, what they intend to do on their test. It should make people nervous when non-transparent regimes, that have announced that they've got nuclear warheads, fire missiles."

Mr. Bush told a news conference at the U.S.-European Union summit in Vienna that North Korea faces further international isolation if it test fires a long-range missile.

Satellite images show that North Korea may be planning a missile launch.

If Pyongyang actually test fires a missile, U.S. officials are said to be considering shooting it down. The United States has 11 ground-based missile interceptors in Alaska and California.

But the missile defense system is not fully operational and officials say it is difficult to destroy a small missile traveling at high speed.

John Isaacs

Critics say the $90-billion U.S. missile defense program is ineffective. John Isaacs is head of the Council for a Livable World, an arms control advocacy group in Washington. "With all the money spent and all the testing and all the tries, we have no idea if the system will work."

Even if the Pentagon could shoot down a North Korean missile, some nonproliferation experts argue that such a response might provoke a strong international reaction.

Robert Einhorn is an international security expert at the Center for Strategic and International Studies in Washington. He says the international community may not see this as a positive step.

Robert Einhorn

"I think world public opinion would tend to be more, or as hostile, toward the U.S. interception as toward the North Korean launch. And if we tried to intercept it and failed, I think that would be a major embarrassment."

The U.S. Missile Defense Agency had planned a test in the Pacific Wednesday, but officials say it is unrelated to tensions with North Korea.