confederator
/kɑnfɪdɪˈreɪtər/Definitions
1. noun
A person who advocates or seeks the formation of a confederation.
“The politician was known as a confederator, pushing for the state’s independence.”
2. noun
A person who joins or supports a confederation, especially one formed by several states or governments.
“The confederator from the neighboring state played a key role in the regional alliance.”