John Kerry, the US secretary of state, has arrived in South Korea as tension with its northern neighbour continues.<br /><br />Kerry's three-day visit, which began on Friday, will also take him to China and Tokyo.<br /><br />The trip comes as Washington tries to press China to deliver a "tough" message to North Korea to rein in its nuclear programme and belligerent rhetoric, a US official said.<br /><br />Al Jazeera's Marga Ortigas reports.
