Yu Woo-ik addressed former members of parliament, the Yonhap news agency reported. He said one problem is that the North Korean government appears to be in flux following the death of Kim Jong Il and succession of his son, Kim Jong Un.
"I urge North Korea again to come forward for dialogue as soon as its internal situation stabilizes," Yu said.
North Korea has threatened a "sacred war" against the south on the grounds its leaders have been defamed. Yu said the government did not respond to invitations last month from South Korea to discuss cross-border family reunions and plans to exterminate pests around tombs in the north.
North Korea has agreed in talks with the United States to freeze nuclear enrichment and to allow inspectors from the International Atomic Energy Agency into the country.