The 'Russian Roulette' singer – who received a touching letter from 26-year-old Seun Adebiyi, a Nigerian athlete who had hoped to compete in the 2014 Winter Games in skeleton sledding, but was diagnosed with Leukaemia during training – has promised to do everything she can to raise awareness of his condition and find him a bone marrow donor.

Rihanna said: "Leukaemia interrupted Seun's dream of being the first Nigerian in the Winter Olympics, but together we can help him make his dream come true. We need to find him a bone marrow donor! Please sign up with DKMS!"

The pop star is working alongside 'Grey's Anatomy' actor Justin Chambers in asking potential bone marrow donors to come forward and help save the life of the Yale Law School graduate.

Seun is astonished both Rihanna and Justin have taken the time to help him.

He said: "I am deeply touched by their plea for donors, not just for me, but for others as well. Their voices are so powerful and it encourages me how they used their influence to raise awareness about this important issue. That was incredible."

Rihanna previously made successful public pleas both last year and in 2008 to help six-year-old Jasmina Anema and 43-year-old Lisa Flynn find bone marrow transplants.