South Korean President Lee Myung-bak has said he wants a firm commitment from Pyongyang to rejoin disarmament talks and to scrap its nuclear arms programme.
A senior U.S. State Department official arrives in Seoul for discussions aimed at prodding the North back to nuclear talks after the state last week raised tensions by firing artillery toward a disputed sea border with the South.
North Korea raised tensions on the Korean peninsula last week as its military fired hundreds of rounds of artillery shells into its waters on its side of the sea border off the west coast.
Analysts say pressure is mounting on the North to end its year-long boycott of the six-way nuclear talks.
Lee has been critical of the two previous summits where the North won pledges for billions of dollars of aid from the South.
North and South Korean officials have been secretly meeting in Singapore and the North Korean city of Kaesong to try to set up a summit, but hit a snag over South Korean prisoners from the 1950-53 Korean War still held in the North.