sideline

not actively involved in something The majority of Western countries decided to stay on the sidelines during the crisis.

to not be actively involved in something The majority of western countries decided to stay on the sidelines during the crisis in the Middle East.

Observing rather than taking part, out of the action, as in Bolivia's neighbors remained on the sidelines, waiting to see which faction in the dispute would prevail . This idiom comes from sports. The sidelines are the two lines defining the sides of the court or playing field and the area immediately beyond them where, in such sports as football, the non-playing team members sit. [First half of 1900s]