You are supposed to say counterpart "to" sth.
I don't know how to expain it in English correctly. Maybe it's just like "something that corresponds to it." " similar reference to sth." or "analogue of sth."
for example "In practice the US is the only economy large enough, flexible enough, and open enough to act as the counterpart to the net current account surpluses accumulated by the rest of the world. "
You may see the preposition "for" in the same sentence with Counterpart. But I guess it has its own meaning and nothing to do with the word "Counterpart".