TOKYO, May 21 (Reuters) - Japan is likely to hold off on administering AstraZeneca PLC's COVID-19 vaccine despite expected approval on Friday, amid concerns about blood clots, public broadcaster NHK and other media reported.

The government it also expected to formally approve on Friday the COVID-19 vaccine developed by Moderna Inc as it seeks to speed up what has been the slowest vaccination campaign among rich countries. (Reporting by Chang-Ran Kim; Editing by Jacqueline Wong)