Q. Can North Korea mount a nuclear attack?
A. Experts disagree about how soon the communist nation can overcome the twin complexities of developing nuclear warheads and perfecting a delivery system.
Some say it could take years. Others warn the North may be well on its way.
Rudimentary test bombs can be the size of small trucks, ruling them out as missile payloads.
''They can deliver it, put it on a cargo ship, drop it from a cargo plane,'' said expert Gordon Chang. ''The point is, can they shrink it to put it on a missile? I don't think they can.''
Q. How big was the blast?
A. Russia and South Korea said seismic measurements showed the force was far weaker than the nuclear bombs dropped on Japan in World War II.
Q. Could an arms race begin?
A. The test could spur non-atomic Japan to increase defense spending or even consider developing its own nuclear deterrent. That could prompt South Korea -- which nurses suspicions about Japanese intentions -- and others like Taiwan to follow suit.
''The test inevitably alters the balance of power,'' said Mark Fitzpatrick of London's International Institute for Strategic Studies.
Q.Is this President Bush's fault?
A. The president long has faced complaints that he has failed to sufficiently address North Korea.
In the nearly five years since Bush labeled North Korea part of an ''axis of evil,'' Kim Jong Il's government has withdrawn from the Nuclear Nonproliferation Treaty, announced it has nuclear weapons, refused to return to six-nation talks and launched seven missiles into the Sea of Japan.
Democrats said Bush was too busy with Iraq to pay attention to North Korea.
Rep. John Boehner (R-Ohio) accused Democrats of standing in the way of work on a missile defense program.
Q. What about the other nuclear wannabe, Iran?
A. How the Security Council reacts to North Korea will be watched ''very carefully'' in Tehran, said Robert Einhorn of the Center for Strategic and International Studies.
''If the U.S. can't build consensus for a tough reaction to North Korea, Iran may see that it can go down the nuclear path with impunity,'' Einhorn said.
