Gates, however, rejected any suggestion that the United States was not in a position to respond militarily to North Korean aggression because it is stretched thin by wars in Iraq and Afghanistan."If there were a problem in Korea, our main arms would be the Navy and the Air Force and those are not stretched in the same way that the ground forces are," Gates told reporters at the Pentagon, adding the U.S. was consulting with Seoul."But again the key thing to remember here is that this was an attack on a South Korean ship. And the South Koreans need to be in the lead in terms of proposing ways forward."South Korea accused the North earlier on Thursday as it announced the results of its investigation into the March sinking of the Cheonan corvehtte, which killed 46 South Korean sailors.Seoul said it would take "firm" measures against its impoverished neighbor. North Korea responded that it was ready for war if Seoul or its allies imposed sanctions.