US Defense Secretary, Jim Mattis has expressed strong caution about the capabilities of North Korean missiles. <br/><br/>In an interview with a Television channel yesterday, he said US assumes that North Korea is getting better with each test. <br/><br/>He called North a direct threat to the United States. He took a cautious stance toward taking military action, saying a military conflict with North Korea would probably be the worst kind of fighting in most people's lifetimes. <br/><br/>He stressed the need to continue seeking a diplomatic solution. Mattis said the US has made it very clear that it is willing to work with China and that he believes China has tried to be helpful in settling the issue.<br/><br/>Meanwhile, the US Defense Department says officials are planning to dispatch the USS Ronald Reagan aircraft carrier to the region to conduct a joint drill with the USS Carl Vinson carrier group which is already maneuvering in waters off the Korean Peninsula.<br/>