Obama says North Korea must show it is serious on talks

US President Barack Obama on Thursday stood by ally South Korea in demanding a change in attitude from North Korea to restart six-party nuclear talks, but held out the prospect of economic aid if it changes. 

The secretive North has said it wants to restart the nuclear disarmament talks it walked out of two years ago, but Seoul and Washington have said the North must first show sincerity in its pledges to denuclearise.

Tensions on the peninsula sank to their lowest level in over a decade in March when the South Korean warship, the Cheonan, was torpedoed, killing 46 sailors. 

An international investigation found the North responsible for the attack, but Pyongyang has said it was not involved.                                           

Obama told a news conference in Seoul that North Korea must address the South''s concerns about the sinking and stop provocative actions. Pyongyang should also fulfil its obligations on eliminating its nuclear weapons programme, he said.                                           

South Korean President Lee Myung-bak told the same news conference that he and Obama "reaffirmed the point that North Korea must show a genuine gesture and responsible attitude on the Cheonan incident and that would be the starting point of improvement in South-North ties".

The United States is one of five regional powers, along with Russia, China, Japan, South Korea, involved in stalled six-party talks on dismantling Pyongyang''s nuclear arms programme.