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Currently, international agreements are executed by executive agreement rather than treaties at a rate of 10:1. Despite the relative ease of executive agreements, the President still often chooses to pursue the formal treaty process over an executive agreement in order to gain congressional support on matters that require the Congress to pass implementing legislation or appropriate funds, and those agreements that impose long-term, complex legal obligations on the United States. For example, the deal by the United States, Iran and other countries is not a Treaty.

The president of the United States might prefer the formal treaty process on matters that require Congress to do what?
pass implementing legislation or appropriate funds