Former South Korean President Kim Dae-jung has postponed a trip planned next week to North Korea, an aide said Wednesday, amid rising tension over the communist nation's apparent moves to launch a long-range missile.

Kim's "trip has become difficult," Jeong Se-hyun, a former unification minister, told a Seoul news conference.

However, Jeong said "North Korea's invitation to Kim Dae-jung is still valid and the two sides will continue contacts."

CountryWatch: North Korea

CountryWatch: South Korea

The South's Kim met North Korean leader Kim Jong Il in June 2000 in the first-and-only ever summit between leaders of the divided Koreas.

The two Kims had been expected to meet again during the scheduled four-day visit, which was being billed as a private trip.

The meeting had raised hopes of creating a channel for dialogue as concerns grow over the North's apparent plans to launch a long-range missile. The North has abided by a self-imposed moratorium on such launches since 1998, but a North Korean diplomat said Wednesday in reported remarks that the ban was only valid while it was having active dialogue with the U.S.

On Tuesday, Kim Dae-jung met the U.S. envoy to South Korea to discuss the trip. U.S. Ambassador Alexander Vershbow said both had agreed that a potential missile launch by Pyongyang "would only further compound North Korea's isolation and put it more apart from the international community."

Kim had hoped to travel to Pyongyang via rail using rebuilt tracks running across the heavily armed border dividing the peninsula. But those plans were dashed last month after the North canceled train test runs at the last minute.

The two Koreas still had agreed that Kim would travel to the North by land, but discussions on final arrangements for the trip had been inconclusive.