Unification Minister Lee Jae-joung says that if next month's test runs of inter-Korean railways flop again, it will fundamentally undermine Seoul-Pyongyang relations.

The two Koreas agreed Sunday to hold the test runs on May 17th.

In a phone interview with KBS radio, the minister said that a safety guarantee by North Korean military authorities would be of utmost importance this time around as well.

But he expected that the test runs would likely take place as the two sides agreed to pursue them in tandem with the joint development of light industry and mineral resources during May and June.

Regarding Seoul's pledge to provide 400-thousand tons of rice aid to Pyongyang from late May, Lee stressed the need for the North to implement the six-way nuclear agreement, reaffirming the link between the two issues.

He said, however, that delivery of the rice aid will begin if the North implements just one of its initial pledges to shut down and seal its nuclear facilities and invite International Atomic Energy Agency inspectors.