John Kennedy actually said...
In Class I-Y shall be placed any registrant who would have been classified in Class I-A or Class I-A-O as being currently available for service in the Armed Forces but for the fact that he has been found to be physically, mentally, and morally qualified for such service only in time of war or national emergency declared by the Congress.
Context
Executive Order 10984—Amending the Selective Service Regulations
01/04/1962