SEOUL, South Korea – South Korea has airlifted 200 tons of mandarins to North Korea in exchange for shipments of pine mushrooms from the North in September, officials said Monday.

South Korean military planes traveled to Pyongyang, capital of North Korea, on Sunday and Monday to deliver the fruits of the southern island of Jeju, according to the Seoul Ministry of Defense. The airlifts are another sign that Moon Jae-in, the South Korean liberal president, is continuing his efforts to improve his relations with North Korea despite the stalemate in global diplomacy over the northern nuclear program.

After a summit meeting between the Koreans in Pyongyang in September, North Korea donated 2 tons of pine mushrooms to South Korea as a gesture of goodwill. Pine mushrooms are white and brown mushrooms that are considered a delicacy for health, both in Korea and other Asian countries. They are one of the most popular regional products of the North. The country shipped them to South Korea in 2000 and 2007, after the previous summit.

After their summit, North Korean leader Kim Jong Un also gave Moon a gift of two dogs, both white Pungsans. On Monday, Moon tweeted that one of the dogs, named Gomi, had given birth to six healthy puppies last Friday.

"Six dogs have been added to a gift of two dogs.I can not help but say that it is a big fortune and I hope South-North links will be like these." said Moon.

Pungsan is a dog breed originally from North Korea and known for his loyalty and courage during the hunt. North Korea sent a pair of Pungsans to South Korea after the 2000 summit, and South Korea gave two Jindo native dogs to the North.

Despite closer ties between the Koreas, there has been no major breakthrough in US-led diplomacy aimed at removing North Korea's nuclear program.

According to officials in Seoul and Washington, North Korea has recently postponed the high-level talks with the United States on the disarmament of the North and the organization of a second summit between President Donald Trump and President Kim.

After a provocative series of nuclear and missile tests last year, North Korea began talks with the United States and South Korea this year, saying it was willing to reduce its arsenal of nuclear weapons in full growth. The North has since taken steps such as the dismantling of its nuclear test site and parts of its rocket engine test facilities, but the US authorities want it to take more significant and irreversible denuclearization.

Moon, who has met Kim three times this year, believes that better ties between the Koreas will help solve the nuclear problem.

The South Korean Ministry of Unification announced Monday that it had approved the visit of seven North Koreans to attend a university forum in the south later this week. The forum focuses on regional issues, including the mobilization of workers from the wartime region of Japan in the Asia-Pacific region.

Seoul announced on Saturday that the two Koreas have finished withdrawing their troops and firearms from some of their front-line guards as part of their agreements to reduce military tensions. The Koreas also ended military exercises along their border and cleared mines in a border area to conduct their first ever joint search for the death of the Korean War.