North Korea has canceled a landmark test of rail links with South Korea one day before it was scheduled to take place. The North Koreans cited a lack of progress in military talks, plus political conditions in the South, as the reason for their decision. South Korean officials are calling the postponement "very regrettable."

South Korean Unification Minister Lee Jeong-seok called an emergency meeting Wednesday after North Korea sent a telegram calling off the railroad test scheduled for Thursday.

South Korean workers clean the railway tracks, which the two Koreas hope to reconnect as a part of an agreement

The test was to involve two short stretches of rail track - one on the eastern side of the peninsula and one in the West - that cross the heavily fortified Demilitarized Zone, which has divided the Koreas for more than 50 years.

Unification Ministry spokesman Shin Eon-sang expressed Seoul's deep disappointment.

Shin says North Korea's unilateral delay of the test is very regrettable, and that full responsibility for the delay lies with Pyongyang. He says he hopes North Korea takes sincere steps to put the rail test back on schedule.

A report by the North Korean Central News Agency Wednesday cited the failure of last week's high-level military talks between the two Koreas as the main reason for the postponement. Generals from the two sides had hoped to reach agreement on a military protocol for the rail test, which passes through sensitive security areas.

Despite the setback, South Korean Defense Minister Yoon Kwang-ung remained positive about the prospects for the rail link.

He says the North's unilateral decision to delay the rail test does not necessarily indicate a decline in North-South relations. He says Unification Ministry officials will be working closely with Pyongyang on the issue in the days ahead.

Yoon was addressing a news conference on South Korean military reform, in which he outlined plans for a smaller, more advanced military by the year 2020.

Former South Korean President Kim Dae-jung, whose landmark summit with North Korean leader Kim Jong Il in 2000 helped open an era of relative cooperation between the two Cold War rivals, is scheduled to make a follow-up visit to Pyongyang next month. Mr. Kim had hoped to make the journey by train.

Wednesday's North Korean announcement also referred to "political conditions" in South Korea as a reason for the postponement. It quoted an unnamed North Korean official as expressing concern over what was described as "pro-United States, ultra-right conservative forces" in the South.

The remark is considered a reference to expectations that South Korea's main opposition party, the conservative Grand National Party, or GNP, is headed for a victory in regional elections scheduled for next Wednesday. A GNP-led government in South Korea would likely make fewer concessions to North Korea than the Uri Party of South Korean President Roh Moo-hyun.