friendly powers; treaty powers
Diplomatic term for nations with which one's country maintains friendly relations or has concluded treaties. Often used in historical or political contexts.
Japan has concluded peace treaties with many friendly powers.
After opening the country in the 19th century, Japan advanced diplomacy with Western treaty powers.
友好国 emphasizes amicable relations, whereas 交際国 is a more formal term often used in the context of diplomatic recognition and treaties.
Compound of 交際 (こうさい, 'association; intercourse') and 国 (こく, 'country'). The term likely emerged in the Meiji era as Japan formalized its diplomatic relations with Western nations.