On March 11th, Minister Wakamiya had a press conference, and announced that Republic of Slovenia has confirmed its participation in the Expo.
This makes in total of 87 countries and 6 international organizations that have confirmed their participation, as of March 11th, 2022.
For the detail, please check the list of participants on the website of Ministry of Foreign Affairs.
Ministry of Foreign Affairs "Confirmed Participants for the Expo2025"
https://www.mofa.go.jp/ecm/ec/page22e_000942.html