South Korea says that a planned summit with North Korea will aid international efforts to end the country's nuclear programme.
Mr Lee described the summit as an 'important opportunity'
Unification Minister Lee Jae-joung said the meeting was an important opportunity to discuss the issue.
The summit, only the second ever between the two sides, is set to take place between 28-30 August.
Key nations have welcomed the move, but South Korea's opposition party has called it an election stunt.
South Korean leader Roh Moo-hyun has less than six months left in office, with presidential elections set for December.
The two Koreas held their first leaders' summit seven years ago, a meeting that brought improved ties between the two sides, who remain technically at war.
Officials will meet in the border city of Kaesong to formalise an agenda for the meeting.
THE TWO KOREAS
1910: Korean Peninsula colonised by Japan
1945: Divided into US-backed South and Soviet-backed North
1950-1953: Korean War, no peace deal signed
1987: North Korea bombs a South airliner, killing 115
1990s: South Korea introduces conciliatory Sunshine Policy
2000: Kim Jong-il and Kim Dae-jung hold first leaders' summit
But Mr Lee said that the summit "will be a very important opportunity for the heads of South and North Korea to actively resolve the North Korean nuclear issue and improve inter-Korean relations".
South Korean President Roh Moo-hyun would also ask to use restored cross-border transport links to travel to Pyongyang, Mr Lee said.
His predecessor, Kim Dae-jung, flew to Pyongyang for his summit, but Mr Lee said that he believed North Korea would accept a request for Mr Roh and his entourage to travel by land. Cross border roads exist and in May, a pair of passenger trains made a one-off crossing over the heavily fortified border - for the first time in more than 50 years.
South Korea has been pushing for the North to allow more regular transport into and through its territory.
Key nations have welcomed Wednesday's surprise announcement, expressing hope that it will benefit the ongoing denuclearisation process.
Last month, Pyongyang shut down its main Yongbyon reactor as part of an international aid-for-disarmament deal. Officials are now hammering out details of the next phase of the deal.
However the Grand National Party, South Korea's main opposition party which advocates a tougher line towards North Korea, has rejected the summit as a ploy aimed at December's presidential polls.
"One suspects that South and North Korea have agreed to hold a summit because the presidents of both countries have the December presidential election on their minds," the JoongAng Ilbo daily said in an editorial.
But other newspapers gave the summit a guarded welcome, the French news agency AFP said.