A South Korean presidential delegation flew to North Korea on Wednesday for talks to arrange a summit planned later this month and help rescue faltering nuclear diplomacy between Washington and Pyongyang.

According to Associated Press, It’s unclear who the South Korean envoys will meet in the North or whether they will see North Korean leader Kim Jong Un before returning to the South later Wednesday.

South Korean President Moon Jae-in said his national security adviser will be carrying a personal letter for Kim. Moon said the envoys are tasked with a crucial role at a “very important time” that could determine the prospects for lasting peace on the Korean Peninsula.

While pushing ahead with summits and inter-Korean engagement, Seoul is trying to persuade Washington and Pyongyang to proceed with peace and denuclearization processes at the same time so they can overcome a growing dispute over the sequencing of the diplomacy.

Seoul also wants a trilateral summit between the countries, or a four-nation meeting that also includes Beijing, to declare a formal end to the 1950-53 Korean War. The U.N. General Assembly in late September would be an ideal date for Seoul, but many analysts see that possibility as low, considering the complications of the process and how far apart the parties currently are.

U.S. officials have insisted that a peace declaration, which many see as a precursor to the North eventually calling for the removal of all U.S. troops from the Korean Peninsula, cannot come before North Korea takes more concrete action toward abandoning its nukes. Such steps may include providing an account of the components of its nuclear program, allowing outside inspections and giving up a certain number of its nuclear weapons during the early stages of the negotiations.