Bollywood actor-producer Aamir Khan was keen to attend British rock band Coldplay39s performance here on Saturday as part of the maiden Global Citizen Festival India, but pre-production work on his film "Dangal" will keep him away.Aamir had backed the event since its official announcement and was looking forward to it, but he is tied down by work for his keenly awaited movie, said a source.The news was confirmed by the actor39s spokesperson.Aamir is all set to release "Dangal", a biopic on the life of wrestler Mahavir Singh Phogat39s journey of mentoring his daughters, who went on to win Olympic medals.With the film, Aamir will also be introducing two new faces to the industry with the launch of Fatima Sana Shaikh and Sanya Malhotra. He is confident about their talent and performance, and so he is completely investing his energy into pre-production work of the film.Presented by Disney, the Aamir Khan Productions movie is directed by Nitesh Tiwari. It will release in December 23.