They may agree, or they may disagree, or even fight. National governments are created by the people, and should, therefore, be the servant of the people. The United Nations was created by the member nations, and should, therefore be the servant of member nations - not the other way around. The concept of equal sovereignty is consistent with, and grows from the principles of freedom. The concept of sovereign equality annihilates the principles of freedom by ignoring the principle that legitimate government power arises from the consent of the governed, which is conveyed through representatives elected by, and accountable to, the people who are governed.
Equal sovereignty recognizes that nations have an equal right to agree, disagree, or even fight.
The parties suffer or benefit as the result of their voluntary decisions. Sovereign equality presumes the power to force compliance with actions prescribed by the sovereign power. When individuals or nations are subject to a power over which they exercise no control, freedom becomes a commodity to be denied in varying measures, by the holder of that power. Freedom, like life itself, is a gift from the Creator. Freedom cannot be granted by any government - it can only be denied by government.