Coming To A Head

When things are "coming to a head," a confrontation or point of crisis is being reached, usually after a long period of build-up.

Example: "Canada Post's urban workers could go on strike late Thursday night if the Crown corporation declines to accept its latest offer, as seven months of heated negotiations between the two sides appears ready to come to a head."

That is, at the time this story was written, the two sides had not "sealed the deal" (reached an agreement successfully); rather, a strike has been called, and Canada's postal workers were set to go on strike within days.