(1) Except as the parties otherwise agree, a party may present an incidental or additional claim or counter-claim,provided that such ancil- lary claim is within the scope ofthe arbitration agreement ofthe parties.

(2) An incidental or additional claim shall be presented not later than in the reply and a counter-claim no later than in the counter- memorial,unless the Tribunal,upon justification by the party present- ing the ancillary claim and upon considering any objection of the other party,authorizes the presentation of the claim at a later stage in the proceeding.