When two warring sides decide to call it quits, it's called a truce — an agreement to end the fighting.
When there's a truce, the two sides stop attacking each other, catch their breath, and try to work out a peace deal. A truce isn't a permanent solution: it's more like a time-out. People with other kinds of conflicts talk about truces, too. If you and your sister are in an ongoing battle, one of you could say, "Can we please call a truce?" That means you'll take a break from squabbling, at least for a while.