North Korea has postponed inter-Korean talks on improving rail links, in a possible sign of unease over South Korea's incoming government.
The two Koreas launched a cargo rail service last year
Working-level officials were due to meet to discuss issues including the newly-launched cross-border cargo link.
But Pyongyang asked for a postponement, citing "time constraints", officials in Seoul said.
The new South Korean leader, who urges a tougher line towards Pyongyang, is due to take office in February.
Pyongyang asked for the two-day talks to be suspended because ""it is the start of the year and there are a few things to prepare", South Korea's Unification Ministry said.
No date was given for the talks to take place, the ministry said.
South Korea is seeking stronger rail links with the North.
A daily freight service was launched in December 2007, connecting the South with a joint industrial zone in Kaesong.
Seoul also wants regular passenger services, as well as wider rail links with North Korea and China, but Pyongyang has opposed this.
The move comes a month before Lee Myung-bak, who won a landslide victory in last year's elections, takes office in Seoul.
The president-elect says future economic packages for North Korea will be linked to progress on the nuclear disarmament issue.
He also plans to close the Unification Ministry - responsible for inter-Korean ties - and conduct relations with Pyongyang through the Foreign Ministry, a move unlikely to please North Korea.