The talks between U.S. President Donald Trump and Japanese Prime Minister Sanae Takaichi came after Tokyo agreed last year to invest $550 billion through 2029 as part of a new trade pact with Washington.
Thursday's joint statement on the so-called small modular reactors (SMRs) also announced a $33 billion investment in natural gas power generation facilities in Pennsylvania and Texas.
The countries announced the first tranche of projects under the new investment fund in February, with $36 billion in commitments in three infrastructure projects.
Thursday's statement said the projects would ensure security by "accelerating economic growth of both countries, thereby paving the way for a New Golden Age of the ever-growing Japan-U.S. Alliance."
It touted the SMRs, built by GE Vernova Hitachi, as providing "a tremendous next-generation stable power source, stabilizing electricity prices for American people and strengthening the Japan-U.S. leadership in global technological competition."
Both sides also released an action plan Thursday on developing critical mineral supply chains, amid concerns about China's dominant role in the sector.
It includes discussing coordinated trade policies and mechanisms, such as border-adjusted price floors, "focusing in the first instance on select critical minerals."