Oh boy, here we go again (today's headline news on cnn.com):

NEW YORK (CNN) -- The United States believes North Korea attempted to detonate a nuclear device and that "something went wrong," a U.S. government official told CNN Tuesday.

The official confirmed North Korea informed the Chinese government prior to the test that it would be a 4 kiloton nuclear device.

The official added that the unexpectedly small blast, of a half kiloton or less, indicated "something went wrong."

Nuclear tests in 1998 by India and Pakistan were about 24 to 50 times as powerful - or in the 15 kiloton range, according to the Federation of American Scientists.

The United States still cannot say for sure the underground detonation was a nuclear blast; the working assumption is that it was, but not very successful, the official said. (Dud or deception? Read the full story)

Another U.S. official said it is possible North Korea may attempt a second test, but cautioned there has been no evidence of any preparations at another test site.

"I would not say we expect it," the official said on condition of anonymity because he is not authorized to speak publicly, "but it would not be a total surprise."

Russia's Defense Minister said Tuesday that his agency has estimated the power of the explosion at between 5 and 15 kilotons.

But the U.S. intelligence community is sticking by an estimate that the blast was approximately a half kiloton, or even less, although it's possible the hardened tunnel in which the test took place could have "muffled" the seismic waves, an official told CNN.