/snip South Korea's Joint Chiefs of Staff Chairman Kim Tae-young told a parliamentary committee Wednesday that he believes the North "has been pushing to develop a small warhead to be mounted on a missile." Kim was quoted as saying by his office that it is unclear whether the North has already manufactured such a small nuclear warhead. North Korea, which conducted an underground nuclear test in 2006, maintains a stockpile of plutonium believed to be sufficient to produce about a half dozen bombs. /snip