342 United Nations — Treaty Series • Nations Unies — Recueil des Traités 1980 (a) The d cision as 10 the action to be iaken in regara to suen proposal; (b) The negotiation and conclusion of any agreement for the amendment of the treaty. 3. Every State entitled to become a party to the treaty shall also be entitled to become a party to the treaty as amended. 4. The amending agreement does not bind any State already a party to the treaty which does not become a party to the amending agreement; article 30, paragraph 4(6), applies in relation to such State. 5. Any State which becomes a party to the treaty after the entry into force of the amending agreement shall, failing an expression of a different intention by that State: (a) be considered as a party to the treaty as amended; and (b) be considered as a party to the unamended treaty in relation to any party to the treaty not bound by the amending agreement. Article 4L AGREEMENTS TO MODIFY MULTILATERAL TREATIES BETWEEN CERTAIN OF THE PARTIES ONLY 1. Two or more of the parties to a multilateral treaty may conclude an agree ment to modify the treaty as between themselves alone if: (a) The possibility of such a modification is provided for by the treaty; or (b) The modification in question is not prohibited by the treaty and: (i) Does not affect the enjoyment by the other parties of their rights under the treaty or the performance of their obligations; (ii) Does not relate to a provision, derogation from which is incompatible with the effective execution of the object and purpose of the treaty as a whole. 2. Unless in a case falling under paragraph l(a) the treaty otherwise provides, the parties in question shall notify the other parties of their intention to conclude the agreement and of the modification to the treaty for which it provides. PART v. INVALIDITY, TERMINATION AND SUSPENSION OF THE OPERATION OF TREATIES SECTION i. GENERAL PROVISIONS Article 42. VALIDITY AND CONTINUANCE IN FORCE OF TREATIES 1. The validity of a treaty or of the consent of a State to be bound by a treaty may be impeached only through the application of the present Convention. 2. The termination of a treaty, its denunciation or the withdrawal of a party, may take place only as a result of the application of the provisions of the treaty or of the present Convention. The same rule applies to suspension of the operation of a treaty. Article 43. OBLIGATIONS IMPOSED BY INTERNATIONAL LAW INDEPENDENTLY OF A TREATY The invalidity, termination or denunciation of a treaty, the withdrawal of a party from it, or the suspension of its operation, as a result of the application of the present Convention or of the provisions of the treaty, shall not in any way impair the duty of any State to fulfil any obligation embodied in the treaty to which it would be subject under international law independently of the treaty. Vol. 1155,1-18232