Something needs all over the world and its current end would definitely put the entire world in trouble is a good example of market imperative. Therefore I have spontaneously thought of oil. Why oil?
At this time, oil is maybe not the most effective source of energy but the one that meet the global demand. Wherever you go today, oil is the source that makes economies grown because it is available in enough quantities and at any time. However, at the rate of the global growth, the end of the reserves is predicted soon.
Moreover, no other reliable sources are yet found. Scientific from all over the world are working on it but, the latest discoveries are not efficient enough to meet global demand such as oil is doing.
On top of the imminent future shortages of oil, these precious sources belong to few nation states, making this global issue harder to solve.
To conclude I can say that oil is an important factor in the international relations.