South Korea has expressed "strong regret" at North Korea's decision to cancel test runs on the cross-border railroad lines between the two countries.

The railroad test was scheduled to be held Thursday under an agreement between the two Koreas made earlier this month.  But the North canceled the test Wednesday because the two sides failed during talks last week to reach agreement on security for the rail lines.

A South Korean government statement urged the North to reschedule the tests as soon as possible.

Rail lines across the inter-Korean border were severed during the Korean War more than 50 years ago, but the two countries have been talking about resuming regular service for years.

Authorities in Seoul say the North Korean military has been reluctant to act on the two countries' political agreement to restore cross-border rail service. 

Some information for this report was provided by AFP and AP.