In the U.S. government, the ultimate authority to approve treaties resides with the Senate. Article II, Section 2 of the Constitution grants the President the power to negotiate and sign treaties, but these agreements require ratification by a two-thirds majority in the Senate. This process is crucial for ensuring that foreign policy aligns with broader national interests and involves legislative oversight. The necessity of Senate approval reflects the principle of checks and balances within the federal system, preventing unilateral action by the executive branch in foreign affairs.