President Donald Trump has again traded barbs with North Korea, shortly before offering to mediate in a heated regional dispute, BBC report.He took to Twitter to complain he would never call North Korean leader Kim Jong-un "short and fat", after its foreign ministry called him "old". It was one of a series of remarks he made on social media before volunteering his services over maritime claims in the South China Sea. "I'm a very good mediator," he said. China, Vietnam, the Philippines, Taiwan, Malaysia and Brunei all have competing claims to territory in the South China Sea. Tensions with China have been high in both Vietnam and the Philippines, inflamed by the formers island-building and naval patrols. A framework for a code of conduct was agreed in August, but this is still only an outline, with more negotiations due to take place before it can be legally binding. Mr Trump, who has long styled himself as a dealmaker, suggested his expertise could aid the process. "If I can help mediate or arbitrate, please let me know," Mr Trump told his Vietnamese counterpart, Tran Dai Quang, at the Asia-Pacific Economic Cooperation summit in Hanoi. Mr Trump's own dispute with North Korea continues to escalate, at least in the insults traded across Twitter and in official statements. On Saturday, North Korea denounced Mr Trump's Asia trip, calling it a "warmonger's visit" and again described the president as a "dotard" - a centuries-old insult for an elderly person. Mr Trump responded with a passive aggressive tweet, suggesting he would never call Mr Kim was "short and fat", and complaining: "Oh well, I try so hard to be his friend - and maybe someday that will happen!"