The Bush administration has said Kim Jong II, leader of North Korea, will "rue the day" he made the decision to go in for the nuclear tests as it (the US) is looking for ways to make it "very costly" for Pyongyang.

"I'm telling you, he (Kim) is going to really rue the day that he made this decision. At this point I'm not prepared to say precisely what the elements are. But I can assure you we're looking for ways to make it very, very difficult, very costly for North Korea to get the technology for these weapons of mass destruction, very difficult for them to get the money for these weapons of mass destruction," Assistant Secretary of State Christopher Hill said in a television interview.

He also indicated that it will intensify the discussions with China with a view to firm up sanctions against Pyongyang to ensure that the punitive measures work.

"I can't speak for the Chinese, but I can assure you we are very much in touch with the Chinese. Secretary Rice was up half the night last night. And one of the prime people that she was talking with were the Chinese. So, we're going to really intensify our consultations with China. China is clearly, clearly upset," Hill said.

"The Chinese have indicated they're going to work with us in New York, and we'll see what we get. But I think we can get something that will be far more than just some sort of angry letter," he added.