Surprisingly, bitter feuds between Japan and its two most influential neighbors seem not to interfere with their cooperation on the problem they all have with North Korea, says the top State Department official who deals with East Asia. Japan's differences with China and South Korea can be traced almost entirely from the Imperial Japanese Army's often brutal occupation of Asia before and during World War II. Almost all Asia came under the Japanese boot, but Korea and China were among those most drastically affected. The latest problems arose this year after Prime Minister Junichiro Koizumi ignored requests by China and paid his fourth annual visit to Tokyo's Yasukuni Shinto shrine, which honors Japan's 2.5 million war dead. Some were executed war criminals, such as World War II Prime Minister Hideki Tojo. The two also have objected bitterly to what they consider whitewashing of the war experience in Japanese schoolbooks. Assistant Secretary of State Christopher Hill told editors and reporters of The Associated Press on Friday that he had misgivings early in the year, "when these issues started bubbling over." He worried that the bad blood among the old enemies would damage the united front the US government wanted to present in six-party talks to persuade North Korea to abandon its nuclear weapons program. China, Japan, the two Koreas, Russia and the United States are involved in the touchy diplomatic exercise. Hill said he found he had not needed to worry. "I'm pleased to say that with respect to the six-party talks, when we get together in the room with all six delegations - also measured by number of times the Japanese delegation and Chinese delegation get together - I am pleased to say it has not had any kind of chilling effect within the six-party process," he said. "I think both sides have a real interest in trying to solve this. It's quite possible that when the two sides have a bilateral problem, they can put that aside in order to solve a problem of mutual interest." That held also for Japan and South Korea, he said, "who also have had difficult bilateral moments, but they work very well within the six-party talks."