India must assert itself in international forums, including the World Trade Organisation, to ensure that the western world is forced to keep its promise of transferring technology and provide resources for environment protection, according to the economist and Special Advisor to the Secretary General of the United Nations, Professor Jeffrey D Sachs. "India, along with China is emerging as a global economic giant. I believe that if the country continues to grow at the present rate, the Indian economy will overtake the US economy in the next 50 years. While growth is good, the country has to ensure that it does not follow the unsustainable model of the western countries like the US," Prof Sachs said in his address at the Delhi Sustainable Development Summit organised by The Energy and Resources Institute (Teri)