fortieth instrument of such action, this Convention shall enter into force on the thirtieth day after the date of deposit by such State or organization of the relevant instrument. Article 39. Amendment 1. After the expiry of five years from the entry into force of this Convention, a State Party may propose an amendment and file it with the Secretary-General of the United Nations, who shall thereupon communicate the proposed amendment to the States Parties and to the Conference of the Parties to the Convention for the purpose of considering and deciding on the proposal. The Conference of the Parties shall make every effort to achieve consensus on each amendment. If all efforts at consensus have been exhausted and no agreement has been reached, the amendment shall, as a last resort, require for its adoption a two-thirds majority vote of the States Parties present and voting at the meeting of the Conference of the Parties. 2. Regional economic integration organizations, in matters within their competence, shall exercise their right to vote under this article with a number of votes equal to the number of their member States that are Parties to this Convention. Such organizations shall not exercise their right to vote if their member States exercise theirs and vice versa. 3. An amendment adopted in accordance with paragraph 1 of this article is subject to ratification, acceptance or approval by States Parties. 4. An amendment adopted in accordance with paragraph 1 of this article shall enter into force in respect of a State Party ninety days after the date of the deposit with the Secretary-General of the United Nations of an instrument of ratification, acceptance or approval of such amendment. 5. When an amendment enters into force, it shall be binding on those States Parties which have expressed their consent to be bound by it. Other States Parties shall still be bound by the provisions of this Convention and any earlier amendments that they have ratified, accepted or approved. Article 40. Denunciation 1. A State Party may denounce this Convention by written notification to the Secretary-General of the United Nations. Such denunciation shall become effective one year after the date of receipt of the notification by the Secretary-General. 38