adjective /mi.di.əˈtɔː.ɹi.əl/
Relating to or befitting a mediator (one who mediates).
Whenever a dispute arises between two nations, each insistent upon its own rights and claims, and refusing all mediatorial efforts at compromise, it is usual that the contest develops into a battle of wits and that the essential issue at stake is relegated to the background.
Wikipedia foundation.