Advanced computer modelling has shown that in the event of an asteroid strike the two nations would suffer loss of life so severe they could never recover.
Both nations are among the 10 most at-risk countries, according to researchers from the University of Southampton who compiled the list using software called called NEOimpactor, short for NASA's ‘NEO’ or Near Earth Object programme.
Developed countries make up the majority of those on the list, but China is there too because of the vast number of people who would die.
The Top 10 is:
In terms of sheer population loss, the US, China, Indonesia, India and Japan are most in danger.