Barack Obama: "North Korea must live up to its obligations"
US President Barack Obama and his South Korean counterpart, Lee Myung-bak, have urged North Korea to return to international nuclear negotiations.
The two leaders, speaking at a joint press conference in Seoul, promised the North major economic aid in return.
They also agreed to make progress on a free trade agreement signed in 2007, which has still not been ratified.
The meeting came on the last day of Mr Obama's Asian tour, which was designed to revive US diplomacy in the region.
He has already visited Japan, Singapore and China.
Mr Obama described Mr Lee as his "good friend" and said his welcome to South Korea had been "spectacular".
The BBC's John Sudworth in Seoul says the visit stressed the close, warm relationship between the conservative Mr Lee and Mr Obama.
Mr Obama said his welcome to South Korea had been spectacular
The US president was greeted by friendly roadside crowds and given a Tae Kwon Do uniform and honorary black belt. He said he was looking forward to a Korean barbecue lunch.
The two leaders reaffirmed their unity of view and approach on the North Korea issue.
They said they were seeking to break the pattern whereby the North would raise tensions, agree to talks and then back off without making progress.
"The thing I want to emphasise is that President Lee and I both agree that we want to break the pattern that existed in the past, in which North Korea behaves in a provocative fashion, and then is willing to return to talk... and then that leads to seeking further concessions," Mr Obama said.
Oct 2006 - North Korea conducts an underground nuclear test
Feb 2007 - North Korea agrees to close its main nuclear reactor in exchange for fuel aid
June 2007 - North Korea shuts its main Yongbyon reactor
June 2008 - North Korea makes its long-awaited declaration of nuclear assets
Oct 2008 - The US removes North Korea from its list of countries which sponsor terrorism
Dec 2008 - Pyongyang slows work to dismantle its nuclear programme, after a US decision to suspend energy aid
April 2009 - Pyongyang launches a rocket carrying what it says is a communications satellite
25 May 2009 - North Korea conducts a second nuclear test
5 August 2009 - Former US President Bill Clinton visits to help secure the release of two detained US journalists
6 October 2009 - North Korea tells China it may be willing to return to six-party talks
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