Mr Tony Blair will visit South Korea on July 20th to meet President Mr Roh Moo-hyun to discuss ways of resolving North Korea's nuclear crisis.
Mr Blair will arrive in South Korea after talks in Japan with Prime Minister Mr Junichiro Koizumi. Afterwards he is expected to fly to China for talks focusing on trade.
Britain is one of the few Western countries with an embassy in the North Korean capital of Pyongyang.
Mr Blair's visit comes as South Korea and its allies in the 1950-53 Korean War are commemorating the 50th anniversary of the truce that ended fighting.
The announcement of Mr Blair's visit comes as South Korea is working to open multilateral talks on the nuclear crisis within the next month or two. But Pyongyang and Washington are still divided on the basic conditions dictating any formal talks.
The North Korean nuclear crisis erupted last October when US officials said Pyongyang had admitted to secretly pursuing an atomic weapons programme.
Mr Blair's previous visit to South Korea was in October 2000 for a summit of Asian and European leaders.