South Korea today vowed to go ahead with a live-fire drill on a border island bombarded by North Korea last month, despite the North's threat to strike back harder. A defence ministry spokesman said there is no change in Seoul's stance with regards to the live-fire exercise. The Yonhap news agency quoted a military source as saying the one-day firing practice scheduled sometime between Today and Tuesday when the weather is expected to improve. North Korea yesterday threatened a new and deadlier attack if the South's marines launch shells into what the North claims as its own waters. It said, the attack will be deadlier than what was made on November 23 in terms of the powerfulness and sphere of the strike. US politician Bill Richardson, who is visiting Pyongyang, described the situation as a “tinderbox”.