"Who would support the re-opening of the factory zone at a time when North Korea is advancing its nuclear and missile programs?" said Song who served as the top diplomat in 2006-2008.

On Feb. 10, 2016, South Korea closed the factory zone in response to North Korea's fourth nuclear test and long-range rocket launch last year.

A possible resumption of the industrial park is likely to emerge as a controversial issue for the next administration, as the project, once hailed as a symbol of inter-Korean reconciliation, would be a violation of U.N. sanctions against North Korea.

"(For the resumption), there needs to be some preceding steps.

The United States needs to signal that it intends to improve ties with North Korea and Pyongyang should also freeze its nuclear and missile programs," Song added.

Former Unification Minister Ryoo Kihl-jae said he also supports the re-opening of the factory zone, but predicted that it would not be easy.

"South Korea needs to gradually revive projects that help restore national unity or humanitarian assistance while clearly stating what it wants North Korea to do through behind-the-scene contact," said Ryoo, who served as the minister handling inter-Korean affairs in 2013-2015.

Former Unification Minister Jeong Se-hyun floated the idea of allowing Chinese or Russian firms to invest in the complex to prevent Pyongyang from arbitrarily running it if it is resumed. He served as pointman on North Korea in 2002-2004.

Ryoo said the issue of resuming the now-suspended joint tour program at Mt. Kumgang on the east coast can be used as a good card in handling the North's nuclear problem.

"We could have told North Korea that Pyongyang should show sincerity in resolving its nuclear program if it hopes to resume the tour program," he said. "But the ministry's suggestion was not accepted in the government's decision-making process."

In 2008, Seoul suspended the Mount Kumgang tours after the shooting death of a South Korean tourist by a North Korean solider at the resort. (Yonhap)