SEOUL (AP) -- The leaders of the rival Koreas exchanged letters expressing hope for improved bilateral relations, which plummeted in the past three years amid a freeze in nuclear negotiations and North Korea's accelerating weapons development.
North Korea's state media said leader Kim Jong Un on Wednesday received a personal letter from outgoing South Korean President Moon Jae-in and replied on Thursday with his own letter appreciating Moon's peace efforts during his term.
Pyongyang's official Korean Central News Agency said Friday their exchange of letters showed their "deep trust." Moon's office also confirmed that he exchanged letters with Kim but didn't immediately say what was said.
Tensions on the Korean Peninsula have risen since a series of North Korean weapons tests this year, including its first flight-test of an intercontinental ballistic missile since 2017 in March, reviving the nuclear brinkmanship aimed at forcing the U.S. to accept it as a nuclear power and to remove crippling sanctions.
South Korea's military has also detected signs that North Korea is rebuilding tunnels at a nuclear testing ground it partially dismantled weeks before Kim's first meeting with then President Donald Trump in June 2018, a possible indicator that the country is preparing to resume nuclear explosive tests.
Moon met Kim three times in 2018 and lobbied hard to help set up Kim's meetings with Trump. But the diplomacy never recovered from the collapse of the second Kim-Trump meeting in 2019 in Vietnam, where the Americans rejected North Korea's demands for major sanctions relief in exchange for dismantling an aging nuclear facility, which would have amounted to a partial surrender of its nuclear capabilities.
Kim has since vowed to bolster his nuclear deterrent to counter "gangster-like" U.S. pressure and sped up his weapons development despite limited resources and pandemic-related difficulties.
North Korea also severed all cooperation with Moon's government while expressing anger over the continuation of U.S.-South Korea military exercises, which were curtailed in recent years to promote diplomacy with the North, and Seoul's inability to wrest concessions from Washington on its behalf.
KCNA said Moon wrote in his letter to Kim that he will continue to support efforts for Korean reunification based on their joint declarations for inter-Korean peace issued after their meetings in 2018.
Kim and Moon shared views that "inter-Korean relations would improve and develop as desired and anticipated by the (Korean) nation if the (North and the South) make tireless efforts with hope," KCNA said.
South Korea's next leader could take a harder line toward Pyongyang. Conservative President-elect Yoon Suk-yeol, who takes office on May 10, has rejected pursuing "talks for talks' sake" with North Korea and vowed to bolster Seoul's alliance with Washington and resume their full-scale military exercises to counter the North's nuclear threat.
Analysts say North Korea is also likely to escalate its weapons demonstrations in coming weeks or months to force a reaction from the Biden administration, which has been focused on Russia's war on Ukraine and a rivalry with China.
Biden's special envoy for North Korea, Sung Kim, traveled to Seoul this week for meetings with senior South Korean officials and said they agreed on the need for a strong response to counter North Korea's "destabilizing behavior."
After maintaining a conciliatory tone for years, Moon's government objected more strongly to North Korea's weapons tests this year, criticizing Kim's government for ending its self-imposed suspension of long-range missile testing and urging a return to diplomacy.
Seoul has also accused North Korea of destroying South Korean-owned facilities at the North's Diamond Mountain resort where they ran tours together until 2008. Kim in 2019 called the South Korean facilities there "shabby" and ordered them destroyed, though the work was delayed by the coronavirus pandemic.