Whenever you are in a situation where two parties oppose each other in some way and demand that you pick a side, the reality is that neither of them are on your side.
This applies on every level from interpersonal to international. If Alice and Bob are having a beef and demands that Eve picks a side, then that means that they value their conflict more than their friendship with Eve.
Similarly, you can have two countries under conflict which recently flared up severely, and they are asking your country, indirectly or directly, to pick a side, either to actively participate or to “show your support”. Your country may enjoy good trade relations with both, or maybe your international relation with either party is neutral at best. Whichever may be the case, if any of them saw you as a friend, they would listen to you when you ask them to end their conflict right now, or they would at the very least not try to involve you in it. If they instead start to make demands, forcing you to “be with us or against us” and start harassing you for something to their benefit, then that is not the action of a friend.