shuttle diplomacy

/SH AH1 T AH0 L D IH0 P L OW0 M AH0 S IY0/
noun
  1. 1

    Use of a neutral third party to negotiate peace between two groups of people that refuse to directly talk with each other.

    โ€œ"The White House denied today that it would conduct quiet "shuttle diplomacy" with Chinese diplomats at the United Nations on matters directly involving Washington and Peking." - New York Times, 1971โ€

Source: https://en.wiktionary.org/wiki/shuttle%20diplomacy