Unless otherwise agreed by the parties, if, without showing sufficient cause,
 

(a) the claimant fails to communicate his statement of claim in accordance with article 23(1), the arbitral tribunal shall terminate the proceedings;
 

(b) the respondent fails to communicate his statement of defence in accordance with article 23(1), the arbitral tribunal shall continue the proceedings without treating such failure in itself as an admission of the claimant's allegations;