Article 25 Entry into Force 1. This Agreement shall remain open for signature by the States listed in the Preamble of this Agreement. 2. This Agreement is subject to ratification, acceptance, approval, or accession. Ratification, acceptance, approval, or accession shall be effected by each State in accordance with its constitutional processes. Instruments of ratification, acceptance, approval, or accession shall be deposited with the Government of the United States, hereby designated as the Depositary. 3. (a) This Agreement shall enter into force on the date on which the last instrument of ratification, acceptance, or approval of Japan, Russia and the United States has been deposited. The Depositary shall notify all signatory States of this Agreement's entry into force. (b) This Agreement shall not enter into force for a European Partner State before it enters into force for the European Partner. It shall enter into force for the European Partner after the Depositary receives instruments of ratification, acceptance, approval, or accession from at least four European signatory or acceding States, and, in addition, a formal notification by the Chairman of the ESA Council. (c) Following entry into force of this Agreement for the European Partner, it shall enter into force for any European State listed in the Preamble that has not deposited its instrument of ratification, acceptance or approval upon deposit of such instrument. Any ESA Member State not listed in the Preamble may accede to this Agreement by depositing its instrument of accession with the Depositary. 4. Upon entry into force of this Agreement, the 1988 Agreement shall cease to be in force. 5. If this Agreement has not entered into force for a Partner within a period of two years after its signature, the United States may convene a conference of the signatories to this Agreement to consider what steps, including any modifications to this Agreement, are necessary to take account of that circumstance.