![Obama Warns North Korea On Nuclear Test](https://s.yimg.com/bt/api/res/1.2/ulE9ydEyzWi22QK9a4lqwA--/YXBwaWQ9eW5ld3M7Y2g9MjQwO2NyPTE7Y3c9NDAwO2R4PTA7ZHk9MDtmaT11bGNyb3A7aD0xMTQ7cT04NTt3PTE5MA--/http://media.zenfs.com/en_uk/News/skynews/presser-grab-1-400x240-20140425-111014-282.jpg)
President Barack Obama, who is in Seoul, has warned North Koreaagainst conducting another nuclear test.
"Threats will get North Korea nothing, other than greater isolation," the US leader said, speaking at a joint news conference with South Korean President Park Geun-hye.
Mr Obama said the US and South Korea stand "shoulder to shoulder" in refusing to accept North Korea's nuclear programme.
Pyongyang threatened last month to conduct a fourth nuclear test, possibly while Mr Obama is in the region.
The White House said it was keeping close tabs on activity at the North's nuclear test site, where commercial satellite imagery this week showed increased activity.
During his visit, Mr Obama will seek to reassure South Korea that he is committed to pressuring Pyongyang to abandon its nuclear ambitions.
Mr Obama arrived at the Blue House, the South Korean equivalent of the White House, on Friday for a busy evening of meetings with Ms Park, including a state dinner.
Mr Obama expressed his condolences over the sunken ferry incident, which has consumed Ms Park's government for more than a week as divers discover yet more bodies.
"As allies, but also friends, we join you in mourning the missing, and especially the young people," the US leader said before the two leaders bowed their heads for a moment of silence.
He said the US stands ready to provide assistance as the rescue effort continues.
The president's overnight stay in Seoul is his second stop on a four-country Asia swing that also includes visits to Malaysia and the Philippines.
Mr Obama flew to Seoul from Japan, a major US ally whose relationship with South Korea has deteriorated over historical resentments stemming from World War II.