Aug 2025 – President Lee Jae Myung holds his first bilateral White House summit with U.S. President Donald Trump, laying the groundwork for deeper security and trade cooperation and signaling Seoul’s intent to pursue advanced nuclear capabilities [2].

Oct 29, 2025 – At a second summit in Gyeongju, President Lee and President Trump issue a joint fact sheet that approves South Korea’s plan for nuclear‑powered attack submarines and pledges U.S. support for civil uranium enrichment and spent‑fuel reprocessing, while Trump publicly “approves the nuclear‑submarine program” [16][21].

Dec 2, 2025 – President Lee Jae Myung tells his cabinet that developing nuclear weapons “would be impossible to gain U.S. or international approval,” warning of sanctions and stressing adherence to the NPT [24].

Dec 2, 2025 – Seoul reaffirms its full commitment to the Nuclear Non‑Proliferation Treaty while moving ahead with the submarine program and civilian fuel‑cycle plans, with IAEA officials confirming ongoing safeguards cooperation [22].

Dec 2, 2025 – Democratic Party leader Jung Chung‑rae meets acting U.S. Ambassador Kevin Kim, describing the alliance as “unbreakable” and citing the recent approval for nuclear‑powered submarines as a milestone [23].

Dec 3, 2025 – President Trump announces formal approval for South Korea to build nuclear‑powered, conventionally‑armed submarines; U.S. diplomat Jonathan Fritz says the “Seoul‑Washington alliance is stronger than ever” and notes complete alignment on North‑Korea policy [21].

Dec 7, 2025 – The South Korean presidential office creates cross‑agency task forces to prepare working‑level talks on nuclear‑powered submarines, uranium enrichment, and defense‑cost sharing, aiming for feasible outcomes in the first half of next year [20].

Dec 10, 2025 – Second Vice Foreign Minister Kim Jina arrives in Washington ahead of the 10th Senior Economic Dialogue, urging the United States to assign a counterpart and begin “substantive discussions” on civil uranium enrichment and spent‑fuel reprocessing [19].

Dec 15, 2025 – National Security Adviser Wi Sung‑lac departs for Washington to discuss post‑summit measures, including “accelerating consultations” on nuclear‑powered submarines, uranium enrichment and spent‑fuel reprocessing [18][17].

Dec 16, 2025 – Wi meets U.S. Secretary of State Marco Rubio, noting that “Australia obtained an exception under Section 91 of the Atomic Energy Act” and suggesting a similar bilateral agreement could enable Korea’s submarine ambitions [14]; the same day he confirms the U.S. backs Seoul’s civilian fuel‑cycle push and nuclear‑submarine plan [16].

Dec 16, 2025 – Wi announces that South Korea will explore a separate bilateral accord with the United States, citing the Australian precedent, to bypass existing civil‑nuclear restrictions while pursuing nuclear‑powered submarines [15].

Dec 18, 2025 – Wi reports “progress in talks” with senior U.S. officials on accelerating implementation of summit agreements, emphasizing the need to expedite civil uranium enrichment, spent‑fuel reprocessing, and a Section 91‑based submarine fuel arrangement [12].

Dec 18, 2025 – The Defense Ministry states it will conclude fuel‑supply negotiations for nuclear‑powered submarines within two years, and will draft a detailed blueprint for the program by next year, while also targeting the second stage of the OPCON transfer schedule for the November 2026 defense chiefs’ meeting [13].

Dec 19, 2025 – Foreign Minister Cho Hyun says the ministry will work to arrange President Lee’s state visit to China in early 2026 and to schedule a timely U.S.–Korea summit, highlighting progress on nuclear‑powered submarines, civilian nuclear energy and shipbuilding [10][11].

Dec 20, 2025 – Wi announces that parallel, “simultaneous” working‑level discussions on civil uranium enrichment, spent‑fuel reprocessing and nuclear‑powered submarines will launch in the new year, with separate task forces ready for each issue [9].

Dec 21, 2025 – Wi reiterates the plan for simultaneous talks, adds that a Section 91 agreement will facilitate submarine fuel transfer, and says he will travel to Japan to discuss trilateral cooperation with Japanese Foreign Minister Motegi [8].

Dec 24, 2025 – South Korea and the United States agree to pursue a stand‑alone nuclear‑submarine cooperation pact; working‑level talks are slated to begin early 2026, and a U.S. delegation will visit Korea to implement the joint fact‑sheet provisions [6][5].

Jan 9, 2026 – South Korea establishes an inter‑agency consultative team, chaired by Rim Kap‑soo, to coordinate upcoming U.S. negotiations on civil uranium enrichment and spent‑fuel reprocessing, aiming to revise the 123 Agreement for standing prior approval [3][4].

Jan 13, 2026 – With President Trump inaugurated on Jan 20, the alliance faces uncertainty; Lee Jae Myung accelerates engagement, while officials push to expand U.S. operational control (OPCON) transfer to Seoul by 2030 and address security modernization, including nuclear‑submarine and civilian nuclear goals [2].

Feb 4, 2026 – Foreign Minister Cho Hyun meets U.S. Energy Secretary Chris Wright in Washington, reaffirming the “urgency of advancing civil uranium enrichment, spent‑fuel reprocessing and acquisition of nuclear‑powered submarines,” and both sides pledge “swift, concrete progress” through earnest working‑level consultations [1].