During an international summit, the US president signs a diplomatic agreement with a foreign dictator. The two leaders write the agreement during the summit, and both sign it before they leave.

A formal treaty negotiated and signed by the president must receive the approval of two-thirds of the Senate before the United States is bound by it. If the Senate refuses to ratify it, the agreement may be unenforceable as a treaty. So the correct choice is “The agreement may be unenforceable if the Senate refuses to ratify it.”

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