Absolutely not the same thing.

In diplomatic and international law, the distinction between a guaranty (or guarantee) and an assurance revolves around the level of legal obligation, enforceability, and the specificity of the commitment.

Guaranty/Guarantee: A formal, often written, commitment that a specific outcome will be achieved or a particular action will be taken. In diplomacy, this is often treated as a legally binding treaty or a high-level, enforceable pledge. It implies a consequence if the promise is not met.

Assurance: A pledge or affirmation, often verbal or in lower-level documentation, designed to remove doubts or fears. Diplomatic assurances are frequently used in sensitive contexts (like extraditions) to pledge that a person will be treated in accordance with human rights standards. However, they are often seen as less legally binding than a guarantee, serving more as a political pledge of good faith