Pronouns referring to national states

What is the gender of national states, or which pronoun do you use to refer to the word "state".
The actual case is the following:

Each of the contracting states shall carry *** own costs associated with the arbitration proceedings

What should the *** be here, "its" or "her" ?
Or what about a "singular their"

Thanks for your comments 

Thanks Clive,
It seems to me that US newspapers often refer to England and France as "her". I would guess that goes for Canada as well.
I tend to prefer "its" over "her" too in this case where the reference is back to the impersonal "each of the states", so thanks for the affirmation.
I am pleased to hear that you think it is ok to use "their" although the use of "singular they/their" may not be clear-cut in this example.
If anybody else is a supporter of "singular they/their", would you use it (always/never/sometimes) when referring to a national state, a town or similar, e.g. "Middletown must buy their own fire engine"
Best regards, Bino