As a spiritual and political leader, the Dalai Lama has spent his life building a nation in exile, but potential disputes over his rightful successor could mean the end of an independent Tibet.

As the 14th Dalai Lama celebrates his 90th birthday with thousands of Tibetan Buddhists, there’s already tension over how the next spiritual leader will be selected. Controversially, the Chinese government has suggested it wants more power over who is chosen.

The 14th Dalai Lama turns 90 on Sunday and is expected to give his clearest signal yet on how his reincarnation will be determined at the event in Dharamshala, India, where the Dalai Lama has lived since fleeing Tibet in 1959 after a failed uprising against Chinese rule.