The ICTRP is a country-led initiative. Clinical trial registration happens when countries seek to improve the transparency of clinical trial research involving nationals of that country, and to be more accountable to the individuals who consent to participate in clinical research, and to better oversee and monitor that research.
A Primary Registry in the WHO Registry Network is a clinical trial registry with at least a national remit that meets WHO Registry Criteria for content, quality and validity, accessibility, unique identification, technical capacity and governance and administration.
To meet WHO requirements for transparency and publication it is only necessary for your trial to be to registered once, in either a Primary Registry or an ICMJE approved registry.