You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Treaty

Context:
Another situation can occur when one party wishes to create an obligation under international law, but the other party does not. This factor has been at work with respect to discussions between North Korea and the United States over security guarantees and nuclear proliferation.

Question:
Parties to a treaty may disagree over a desire to create an obligation under what?

international law