Query: What countries agreed to a tripartisan agreement?
Context: After Germany entered a Tripartite Pact with Japan and Italy, Ribbentrop wrote to Stalin, inviting Molotov to Berlin for negotiations aimed to create a 'continental bloc' of Germany, Italy, Japan and the USSR that would oppose Britain and the USA. Stalin sent Molotov to Berlin to negotiate the terms for the Soviet Union to join the Axis and potentially enjoy the spoils of the pact.