Overview: Treaty vs. Agreement in the United States

With respect to international law, Treaties and Agreements are equivalent.

In the United States, the term "treaty" refers to any International Agreement that was made with the "advice and consent" of the Senate. Agreements, on the other hand, do not go through the Senate for "advice and consent" (requiring a 2/3rds majority to approve).

Treaties and International Agreements may be self-executing or may require implementing legislation.

Agreements

Agreements occur in three ways:

  1. Congressional-executive (or, "statutory") agreements, with concurrence from a simple majority of both Houses. Add "agreement" to a search of Congressional documents.
  2. Agreements pursuant to already ratified treaties.
  3. Sole-executive (no involvement by Congress).
    Executive Agreements on the Sole Constitutional Authority of the President, posted to the Legal Information Institute, states that the Executive Agreement is the most common instrument of foreign policy. 

Treaties

  1. Negotiation (conducted by the Executive Branch)
  2. President submits concluded treaty to the Senate for "advice and consent." Treaty is assigned a Document number and referred to the Senate Foreign Relations Committee (with the exception of trade agreements). Treaty text is then printed and made available to the public.
  3. Treaty remains "pending" during which time the committee may conduct hearings, receive comment, and prepare a report. When there is a lack of consensus on a treaty, it may remain "pending" indefinitely.
  4. Report is sent to the full Senate. Must receive 2/3rds majority. If approved, the Senate sends a "resolution of ratification" to the President, sometimes with conditions. In some cases, the conditions will be rejected by the President.
  5. The President, not the Senate, ratifies the treaty (with the consent of the Senate)

References

Kirgis, Frederic L. "International Agreement and U.S. Law." Insights. 2(5), 1997.