The South Korean Unification Ministry said Monday that a working-level meeting between Seoul and Pyongyang scheduled for this week has been postponed indefinitely.

The two sides were scheduled to hold the meeting in Kaesong, the border city of the Democratic People's Republic of Korea (DPRK), on Tuesday and Wednesday to discus railway cooperation projects. However, the DPRK side asked to postpone the meeting due to "time constraints," the Unification Ministry said.

Pyongyang announced the decision in a letter sent to Seoul through its liaison officer at the inter-Korean border village of Panmunjom, the ministry officials told local media.

South Korea's Yonhap News Agency said the DPRK's move had been anticipated as they have kept silent on the inauguration of South Korea's new President Lee Myung-bak on Feb. 25.

Lee's transition team unveiled a plan to merge the Unification Ministry into the Foreign Affairs Ministry as part of efforts to streamline the government. Pyongyang has yet to officially comment on Lee and the merger plan.

Lee has promised to "implement" inter-Korean cooperation projects agreed during an October summit between South Korean President Roh Moo-hyun and DPRK top leader Kim Jong-il after studying their "feasibility."

Seoul and Pyongyang have agreed to discuss cooperation projects in the fields of natural resources, agriculture and fisheries, environmental protection, forestry, weather forecast and public health between January and February.

A joint field study on establishing an inter-Korean economic area in and around the DPRK's port city of Haeju is also scheduled for this month.