US President Barack Obama arrives in Seoul for a visit amid mounting concern that North Korea may be planning another nuclear test.<br/> <br />South Korea rolled out the red carpet for Obama, on the second stop of his Asian tour, arriving from Japan.<br/> <br />Top of the agenda is set to be talks with South Korean leader Park Geun-hye on North Korea after reports of activity at a nuclear test site there.<br/> <br />(SOUNDBITE)(English) UNITED STATES PRESIDENT, BARACK OBAMA, SAYING:<br/> <br />"The United States and South Korea stand shoulder to shoulder, both in the face of Pyongyang's provocations and in our refusal to accept a nuclear North Korea. Threats will get North Korea nothing other than greater isolation."<br/> <br />North Korea has carried out three nuclear tests in the past. The last one in February 2013 triggered months of heightened tension on the Korean peninsula.<br/> <br />During his South Korean tour, Obama is also expected to discuss Seoul's ties with Japan. The US wants its two main Asian alli
