SEOUL, South Korea — The prime ministers of North and South Korea met today for the first time in 15 years, hoping to extend the detente fostered by the second summit of their leaders last month with new South Korean investment in the impoverished North.

North Korean Prime Minister Kim Yong Il said after arriving in Seoul on a direct flight from Pyongyang that he thought the three days of talks would "go well in a warm atmosphere" based on his welcome.

The two sides last held prime ministerial talks in 1992 that were suspended amid the first crisis over the North's nuclear weapons program.

Kim ranks below the top members of the North's ruling elite: leader Kim Jong Il and the country's No. 2 official Kim Yong Nam. He is meeting with South Korean Prime Minister Han Duck-soo, who is the deputy of South Korean President Roh Moo-hyun.

This week's talks are aimed at fleshing out an agreement that Roh and the North Korean leader signed at their October summit in Pyongyang — only the second such meeting since the Korean Peninsula was divided more than half a century ago.

Praising that agreement as a big step toward reconciliation, the North Korean delegation stressed today the importance of taking action.

"No matter how good an agreement is, it ends up an empty piece of paper unless carried out," the North Koreans said in an arrival statement.

This week's negotiations focus mainly on economic cooperation projects, including setting up a joint fishing area around their disputed western sea border and establishing a joint economic area on the North's southwestern coast.

Also on the agenda are building joint shipyards in the North and improving convenience for South Koreans working at a joint industrial zone in the North Korean border city of Kaesong by simplifying border customs inspection and improving communication networks at the zone.