Seoul’s deal with Trump now hinges on two powers in Washington

The two centers of power are the Trump White House and the incoming Democratic-controlled US Congress. The White House negotiated the November 2025 joint fact sheet, while Congress will scrutinize how its commitments are carried out. This matters because the deal’s promises are already connected in practice, even though they are not legally conditional on one another.

South Korea first dealt with the Trump administration alongside a Republican-controlled Congress. Now, as former ambassador Cho Hyun-dong explained, Seoul must manage two centers of power. Congress can use legislation, funding decisions, and investigations to examine or slow implementation, while Trump retains broad authority over foreign policy.

The result could be prolonged uncertainty. Cho warned that stronger congressional oversight could make commitments take longer, especially the investment arrangements. At the same time, a politically weakened Trump may still pursue unpredictable unilateral diplomatic moves. Seoul therefore faces difficult diplomacy for at least the next two years.

The November 2025 joint fact sheet assembled several major commitments into one diplomatic package. South Korea pledged $350 billion in investment in the United States. In return, the package included tariff concessions, US backing for nuclear-powered submarines, and a path toward civilian uranium enrichment and spent-fuel reprocessing.

The commitments are not legally conditional on one another. In practice, however, their implementation has become intertwined. South Korea’s investment projects and the security cooperation it seeks are therefore moving through the same difficult political process. The fact sheet’s nuclear provisions also leave important details unresolved, especially fuel sourcing and legal requirements.

That gap between promises and delivery is now central to the agreement’s future. Investment delays have already held up security discussions, which have effectively stalled since the allies’ first meeting in early June. A Democratic-controlled Congress could add further scrutiny, particularly to the nuclear elements.

South Korea’s promised investment in the United States totals $350 billion, making it the central economic contribution in the joint fact sheet. The scale matters because Seoul is using that contribution to pursue major trade and security benefits from Washington. The package links economic cooperation with sensitive nuclear commitments.

The benefits Seoul seeks include US tariff concessions, backing for nuclear-powered attack submarines, and a path toward civilian uranium enrichment and spent-fuel reprocessing. Shin Kak-soo described the fuel-cycle rights and submarines as key benefits South Korea sought from its investment. The fact sheet approves the submarine plan in principle but leaves fuel sourcing for later discussion.

Delivery remains uncertain. Investment projects have been delayed, and those delays have held up security cooperation. Nuclear cooperation also faces US legal requirements and possible congressional resistance. As a result, South Korea’s large financial promise has not yet produced all the strategic gains it expected.

South Korean investment delays have held up nuclear cooperation because the deal’s separate commitments have become intertwined in practice. Seoul’s investment is the main contribution under the joint fact sheet, while nuclear-powered submarines and civilian fuel-cycle rights are major benefits it seeks. Slow progress on one side has therefore weakened momentum on the other.

The mechanism is political rather than a formal legal condition. The fact sheet does not state that investment must be completed before nuclear cooperation can proceed. Yet discussions on security cooperation have effectively stalled since the allies’ first meeting in early June, and South Korea’s National Security Office has acknowledged that delayed projects contributed to the impasse.

This creates a cycle of delay. Washington may hesitate while investment arrangements remain unsettled, while Seoul waits for clearer movement on nuclear benefits. The problem could grow if Congress increases oversight, making both the investment commitments and nuclear discussions slower to implement.

The US Congress can review and influence a foreign-policy agreement through legislation, appropriations, and investigations. Legislation can establish or change legal requirements. Appropriations control funding for activities that need congressional money. Investigations give lawmakers a way to scrutinize executive actions and demand information.

These tools can affect how quickly or fully an agreement is implemented. The article gives nuclear cooperation as an important example. Civilian enrichment and spent-fuel reprocessing remain subject to US legal requirements, while cooperation on nuclear-powered submarines could require a new bilateral nuclear cooperation agreement, depending on its scope. Congress can therefore examine and shape the legal and financial framework.

However, Congress cannot easily control every foreign-policy move. The president retains substantial authority over foreign policy, and the article says Congress has limited powers in this area. Democrats may still use their other checking tools to increase oversight, delay implementation, or complicate parts of the deal.

Democratic lawmakers’ focus on nuclear nonproliferation could delay South Korea’s nuclear plans because they may apply closer scrutiny to activities involving nuclear technology and fuel-cycle rights. Lee Sang-hyun said Democrats in Congress take a strong position on nonproliferation. That creates a political obstacle even where the White House has made broad commitments.

The fact sheet approves South Korea’s plan to build nuclear-powered attack submarines, but it does not settle how the submarines will obtain nuclear fuel. Civilian uranium enrichment and spent-fuel reprocessing also remain subject to US legal requirements. The Congressional Research Service noted that submarine cooperation could require a new bilateral nuclear cooperation agreement, depending on its scope.

These unresolved details give Congress multiple points for review. Lee expects US-Korean nuclear cooperation and the submarine program could be delayed considerably longer than anticipated. The same scrutiny could slow Seoul’s pursuit of enrichment and reprocessing, despite the investment package.

The United States can negotiate an international agreement through the president, but delivery may depend on Congress. The president retains substantial authority over foreign policy, giving the White House room to make diplomatic commitments and pursue dialogue. Congress, however, can shape the laws, funding, and oversight surrounding those commitments.

The joint fact sheet shows how this division works. The Trump administration backed South Korea’s nuclear-powered submarine plan and outlined cooperation on enrichment and reprocessing. Yet submarine cooperation could require a new bilateral nuclear agreement, depending on its scope. Enrichment and reprocessing remain subject to US legal requirements, while Congress can use legislation, appropriations, and investigations.

Therefore, presidential promises may not translate quickly into completed programs. A Democratic-controlled Congress could increase scrutiny and slow implementation, especially on nuclear issues. At the same time, Trump could continue unilateral foreign-policy moves because Congress has limited powers in foreign policy. The result is uncertainty over both timing and substance.