The arbitration clause contained in a procurement contract also applies in respect of supplementary or amending instruments to the original contract which are in the nature of an addendum, inasmuch as the obligations arising therefrom find their basis in the original contractual relationship.
In the absence of an express intention to the contrary, an arbitration clause must be interpreted as referring to the jurisdiction of the arbitral tribunal all disputes relating to claims whose causa petendi lies in the contract to which the clause is annexed.