A picture taken on February 21, 2017 shows a cake bearing a portrait of Zimbabwe's President Robert Mugabe during a private ceremony to celebrate Mugabe's 93rd birthday in Harare. Mugabe, the world's oldest national ruler, turned 93, using a long and occasionally rambling interview to vow to remain in power despite growing signs of frailty. / AFP / Jekesai NJIKIZANA (Photo credit should read JEKESAI NJIKIZANA/AFP/Getty Images)

A picture taken on February 21, 2017 shows a cake bearing a portrait of Zimbabwe's President Robert Mugabe during a private ceremony to celebrate Mugabe's 93rd birthday in Harare. 


Mugabe, the world's oldest national ruler, turned 93, using a long and occasionally rambling interview to vow to remain in power despite growing signs of frailty. / AFP / Jekesai NJIKIZANA        (Photo credit should read JEKESAI NJIKIZANA/AFP/Getty Images)