Tonga and the Soviet Union established formal diplomatic relations in April 1976.

In the mid-1970s, the entirety of Oceania was firmly aligned with the Western Bloc in the context of the Cold War, and the Soviet Union, despite its eastern coast being on the Pacific Ocean, was excluded from participation in regional matters.

Tonga, meanwhile, had recently regained full sovereignty after being a protectorate of the United Kingdom and was establishing its own foreign policy.

[2][3] Tonga's move to establish relations with the USSR caused alarm in New Zealand,[4][5] the United Kingdom,[6] and West Germany[7] and resulted in several offers of aid from western countries,[8][9] including West Germany.

In 1987, Tonga "played the Soviet card" again (in the words of E. Huffer), when the then crown prince Sia'osi Taufa'ahau Manumata'ogo Tuku'aho Tupou paid a state visit to the Soviet Union,[11] and declared while in Moscow that "Tonga and the Soviet Union are linked, not separated, by the Pacific Ocean", adding that "the USSR [is] a Pacific nation with legitimate interests in the region".