President George Bush and South Korean leader Roh Moo-hyun have said talks should be held to draw up a formal Korean peace treaty.
The two men called for talks on a Korean peace treaty
The 1950-53 war, which left the Korean peninsula divided, was ended with an armistice and North and South are still technically at war.
Both leaders hoped talks on the North Korean nuclear crisis and a peace treaty would complement each other.
They insisted that a nuclear-armed North "will not be tolerated".
Mr Bush is in South Korea as part of an eight-day tour of East Asia. He has already visited Japan and his itinerary includes China and Mongolia.
Mr Bush and Mr Roh met in the ancient Korean capital of Gyeongju for talks and will later join a host of other regional leaders for the Asia-Pacific Economic Co-operation (Apec) summit.
About 250 demonstrators, carrying "Stop Bush" banners gathered at the city's train station to protest at the president's visit.
The two leaders said in a statement a peace treaty would "improve confidence and reduce military tension on the Korean peninsula".
Both countries are publicly committed to seeking a non-nuclear Korean peninsula.
Chinese President Hu Jintao, who is on a state visit to Seoul, said he supported the eventual reunification of the two Koreas.
Mr Bush and Mr Roh said that the nuclear stand-off with the North should be resolved by "peaceful and diplomatic means".
BUSH ON TOUR
"We reiterated that a nuclear-armed North Korea will not be tolerated," President Roh said.
The US and South Korea along with China, Russia and Japan are engaged in negotiations to try to persuade Pyongyang to give up its nuclear programme.
Mr Bush said the US would not consider Pyongyang's demand for a light-water reactor - a stumbling block in the talks - until North Korea disarms.
"We'll consider the light-water reactor at the appropriate time," Mr Bush said.
"The appropriate time is after they have verifiably given up their nuclear weapons and/or programmes."
From South Korea Mr Bush will head to Beijing for talks with the Chinese President Hu Jintao, who will also attend the Apec summit.
Speaking in Japan on Wednesday before flying to South Korea, Mr Bush urged China to embrace more political and religious freedoms.
He compared the strict governmental control in China to the more democratic regime in Beijing's arch-enemy, Taiwan, in a speech correspondents said was likely to irritate the Chinese leadership.