The UN in a Nutshell

This is described as an "old quip," but it's new to me:

When there is a dispute between two small nations, the UN steps in and the dispute disappears. When there is a dispute between a small nation and a large nation, the UN steps in and the small nation disappears. When there is a dispute between two large nations, the UN disappears.

From Ken Rogoff, who suggests some parallels with the IMF.