The South Korean government said Friday that it is difficult to pinpoint who led North Korea's deadly sinking of the warship Cheonan in 2010, amid controversy surrounding a planned visit by a senior Pyongyang official widely suspected of masterminding the attack.

Kim Yong-chol, a top North Korean official, is scheduled to arrive in the South on Sunday for a three-day visit leading a high-level delegation to the PyeongChang Winter Olympics' closing ceremony to be held later in the day. Conservatives and families of the 46 victims of the attack strongly oppose his visit.

"It is clear that North Korea was blamed for the South Korean warship's sinking and Kim was leading North Korea's reconnaissance bureau at that time," Baik Tae-hyun, spokesman at Seoul's unification ministry, told a press briefing.

"But it is also the fact that there is a limitation in pinpointing who was responsible for the incident."

The Cheonan corvette sank on March 26, 2010, near the de facto maritime border in the Yellow Sea, leaving 46 sailors aboard dead. A Seoul-led international commission concluded it was torpedoed by a North Korean submarine, but the North has denied the claim.

The 72-year-old Kim currently leads the ruling Workers' Party of Korea's United Front Department, a unit in charge of relations with the South.

Gen. Kim, a known hard-liner, is suspected of having orchestrated the attack on the Cheonan when he was chief of North Korea's reconnaissance bureau, which is tasked with overseas intelligence operations and cyberwarfare.

It is said that he was also behind other provocations against the South, including the 2010 shelling of Yeonpyeong Island near the western maritime border and the planting of land mines across the inter-Korean border that severely injured two South Korean staff sergeants in August 2015.

The ministry spokesman said that the government is well aware of people's concerns about its acceptance of the Kim-led delegation but called for public understanding of Seoul's decision, which is aimed at improving inter-Korean ties.

"But because the North said the group's trip is to attend the Olympics' closing ceremony and the government believes that its visit will help improve inter-Korean ties and pave the way for dialogue for peace, Seoul has decided to accept Kim's trip," Baik said.

He stressed Kim currently oversees inter-Korean affairs and has a say over the issue of the North's nuclear program.

"The government seeks to focus on who could lead practical dialogue to improve inter-Korean relations and bring peace to the Korean Peninsula, rather than to concentrate on who did what in the past," it said in a statement.

Asked whether the government will challenge Kim over the sinking of the Cheonan during his visit, the ministry said that it will "comprehensively" discuss an enhancement of inter-Korean ties and ways to bring peace to the region.

The Ministry of National Defense declined to comment on the controversy surrounding Kim.

Seoul's defense ministry told foreign reporters in 2010 that the North's Reconnaissance General Bureau was "highly likely" involved in the warship sinking, given the track record of its role in major terror attacks targeting South Koreans, though it could not clearly conclude that the bureau masterminded the naval attack.

"At that time, the ministry raised such a possibility, but it did not make an official conclusion," the ministry's spokesperson Choi Hyun-soo said at a press briefing Friday.

By the same token, South Korea's spy agency told lawmakers that it is not clear that Kim ordered the torpedoing of the ship.

"Political consideration is not being taken into account," the National Intelligence Service was quoted as saying by an opposition lawmaker, when asked whether Kim's trip could drive a wedge among South Koreans.

Kim is blacklisted under Washington's and Seoul's unilateral sanctions. In August 2010, the United States imposed sanctions on Kim and three entities, including the Reconnaissance General Bureau, following the warship's sinking.

In March 2016, Kim was added to Seoul's unilateral sanctions list, due to his alleged role in its nuclear and missile development programs.

But the South said his trip would not be problematic as the sanctions involve an asset freeze, not a travel ban.

Meanwhile, the Ministry of Unification was vague, when asked whether Seoul's spy agency NIS is a counterpart to the WPK's department headed by Kim.

A senior official at Cheong Wa Dae told reporters Thursday that the head of the WPK's United Front Department is equivalent to the chief of South Korea's spy agency.

Some speculate that long-disconnected hotlines reportedly installed at the NIS and the WPK's unit may have been restored in the course of a flurry of sports diplomacy over the North's participation in the Olympics.

Some experts said that the ministry handling inter-Korean affairs appears to be shunning away from ongoing behind-the-scene discussions with the North.

"The NIS and the unification ministry are cooperating with each other," Baik said.(Yonhap)