About 200 South Koreans and their family members prepared to cross into North Korea on Monday for heart-wrenching meetings with relatives most have not seen since they were separated by the turmoil of the Korean War.

The week-long event comes as the rival Koreas boost reconciliation efforts amid a diplomatic push to resolve a stand-off over North Korea’s drive for a nuclear weapons programme that can reliably target the continental United States.

The temporary reunions are highly emotional because most of those taking part are elderly people eager to see their loved ones once more before they die.

Most of the families were driven apart during the 1950-53 Korean War, which ended in a cease-fire, not a peace treaty, leaving the Korean Peninsula still in a technical state of war.

Buses carrying the elderly South Koreans attending this week’s reunions arrived at a border immigration office on Monday morning.

South Koreans in a bus prepare to leave for North KoreaSouth Koreans in a bus prepare to leave for North Korea (Lee Ji-eun/Yonhap via AP)

After undergoing immigration checks, they were to cross the border by bus and travel to the Diamond Mountain resort.

Past reunions have produced powerful images of elderly Koreans crying, embracing and caressing each other. Nearly 20,000 people have participated in 20 rounds of face-to-face reunions held between the countries since 2000.

Another 3,700 exchanged video messages with their North Korean relatives under a short-lived programme from 2005 to 2007. No one has had a second chance to see their relatives.

According to Seoul’s Unification Ministry, 197 separated South Koreans and their family members will take part in the first round of reunions that run from Monday to Wednesday. Another 337 South Koreans will participate in a second round of reunions from Friday to Sunday.

South Korea will also send dozens of medical and emergency staff to Diamond Mountain to prepare for potential health problems considering the large number of elderly participants.

North Koreans prepare to leave for North KoreaAbout 200 South Koreans and their family members will cross into North Korea on Monday (Korea Pool/Yonhap via AP)

Many of the South Korean participants are war refugees born in North Korea who will be meeting their siblings or the infant children they left behind, many of them now into their 70s.

During the three years since the reunions were last held, the North tested three nuclear weapons and multiple missiles that demonstrated a potential of striking the continental United States.

North Korea has shifted to diplomacy in recent months. Leader Kim Jong Un and South Korean President Moon Jae-in, a son of North Korean war refugees, agreed to resume the reunions during the first of their two summits this year in April.

South Korea sees the separated families as the largest humanitarian issue created by the war, which killed and injured millions and cemented the division of the Korean Peninsula into the North and South. The ministry estimates there are currently about 600,000 to 700,000 South Koreans with immediate or extended relatives in North Korea.

But Seoul has failed to persuade Pyongyang to accept its long-standing call for more frequent reunions with more participants.