South Korea will push for the gradual opening of regular rail service with North Korea, the South's official in charge of relations with the North said Monday, ahead of a landmark railway test across their heavily fortified border.

The divided Koreas agreed last week on security arrangements for the one-time test, enabling the first train crossing of their border in more than half a century.

The two Koreas have reconnected two rail tracks and two adjacent roads on each side of the peninsula as part of reconciliation projects launched after their leaders held a breakthrough summit in 2000.

The test scheduled Thursday is to be a single run of two trains, but Seoul hopes it will lead to a gradual opening of rail service between the sides, with the lines eventually linked to Russia's Trans-Siberian railroad.

"We will make efforts to ensure that the opening of railroads and regular service are made at an early date after the test runs," Unification Minister Lee Jae-joung told a news conference.

He said regular rail service to two major joint projects - an industrial complex in North Korea's border city of Kaesong and a tourism venture at the North's Diamond Mountain resort - would boost fledging inter-Korean economic cooperation.

Choson Sinbo, a pro-North Korean newspaper in Tokyo that is considered a government mouthpiece, also hailed the relinked railroads, saying they would contribute to economic development of the two Koreas and give them a leading position in transportation and logistics in Asia and Europe.

Full rail service, however, is unlikely to be restored anytime soon because the two sides need to address a number of issues, such as the modernization of North Korea's dilapidated railroad system.

Also Monday, some 40 anti-North Korean activists held a rally protesting the upcoming rail test near the western military buffer zone separating the two Koreas. They later peacefully dispersed.

The two sides have agreed to reduce the number of people who will board the trains for the railway test, the ministry said earlier Monday.

South Korea had proposed that 200 people - 100 from each of the two Koreas - board each of the two trains. One train is to depart from the South and the other from the North and then return to their origins later in the day.

But North Korea rejected the proposal, citing an unspecified internal issue, according to the ministry.

In working-level talks in Kaesong on Sunday, the two sides agreed that 150 people - 100 South Koreans and 50 North Koreans - will board each of the five-car trains, the ministry said.

The two sides plan to exchange the lists of passengers Wednesday.

Separately, 440 South Koreans returned home after reuniting with 100 North Korean relatives, whom they had not seen since the end of the 1950-53 Korean War, at the end of the latest session of family reunions at the North's Diamond Mountain resort.

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