New Delhi: The United Nations is celebrating the sanitation gains made in India since Prime Minister Narendra Modi came to power in 2014 at a summit this week in New Delhi, but in Tamu Nagar, a slum just outside one of the city's poshest neighborhoods, hundreds of people rely on a single public toilet.

The numbers in the government's ambitious Swachh Bharat, or Clean India, program are staggering. India's population of 1.3 billion constituted 60% of the world's open defecation in 2014 when Modi was elected, but only 20% by 2018.

The $20 billion program concludes in 2019.

But the summit — with a keynote address by UN Secretary-General Antonio Guterres on Tuesday — overshadows the struggles with open defecation that remain in the heart of India's capital.