Artikel XVIII

1. The present Agreement shall be ratified and the instruments of ratification shall be deposited as soon as possible with the Government of the United States of America, which shall notify each signatory State of the date of deposit thereof.
2. Thirty days after four signatory States have deposited their instruments of ratification the present Agreement shall come into force between them. It shall come into force for each other signatory State thirty days after the deposit of its instrument of ratification.
3. After it has come into force, the present Agreement shall, subject to the approval of the North Atlantic Council and to such conditions as it may decide, be open to accession on behalf of any State which accedes to the North Atlantic Treaty. Accession shall be effected by the deposit of an instrument of accession with the Government of the United States of America, which shall notify each signatory and acceding State of the date of deposit thereof. In respect of any State on behalf of which an instrument of accession is deposited, the present Agreement shall come into force thirty days after the date of the deposit of such instrument.