(1) The Respondent may submit a counterclaim at any time during the arbitral proceeding. However, if a counterclaim is filed late in the proceeding and has an undue effect on the other party or delays the completion of the proceeding, then the Tribunal may, pursuant to the other party's request or at its own discretion, deny filing of such counterclaim.
(2) The proceedings of the Respondent's counterclaim shall be annexed to the Claimant's request for arbitration.  
(3) The provisions of Article 10 through Article 13 shall apply mutatis mutandis to the acceptance of a counterclaim, its notice and the answer thereto.

Article 15. Request by Tribunal for Filing of Counterclaim

When the Tribunal decides that the Respondent's defence includes the grounds as well as the purport of a counterclaim, the Tribunal may request to the Respondent that a clarification be made as to whether such counterclaim would be filed as provided in Article 14.