At the same time as it established a peacekeeping force, the Security Council also recommended that the Secretary-General, in consultation with the parties and the Guarantor Powers, designate a mediator to take charge of formal peacemaking efforts. U Thant, then the UN Secretary-General, appointed Sakari Tuomioja, a Finnish diplomat. While Tuomioja viewed the problem as essentially international in nature and saw "enosis" as the most logical course for a settlement, he rejected union on the grounds that it would be inappropriate for a UN official to propose a solution that would lead to the dissolution of a UN member state. The United States held a differing view. In early June, following another Turkish threat to intervene, Washington launched an independent initiative under Dean Acheson, a former Secretary of State. In July he presented a plan to unite Cyprus with Greece. In return for accepting this, Turkey would receive a sovereign military base on the island. The Turkish Cypriots would also be given minority rights, which would be overseen by a resident international commissioner. Makarios rejected the proposal, arguing that giving Turkey territory would be a limitation on "enosis" and would give Ankara too strong a say in the island's affairs. A second version of the plan was presented that offered Turkey a 50-year lease on a base. This offer was rejected by the Greek Cypriots and by Turkey. After several further attempts to reach an agreement, the United States was eventually forced to give up its effort.