NEW DELHI (AFP) - India said on Thursday it would seek the extradition of a Pakistani-American held in the United States to face charges over last years attacks in Mumbai which killed 166 people. Home Secretary Gopal Pillai said the process would begin after an Indian investigation into David Coleman Headleys suspected links to the 2008 militant attacks. We expect that investigations will take about four to six weeks, Pillai said. Once we file the charge sheet, we will definitely be seeking access both for interrogation and [at] a subsequent stage for his extradition. Headley, appearing in a Chicago court on Wednesday, denied helping plan the Mumbai attacks or plotting to attack a Danish newspaper which published blasphemous cartoons. Prosecutors said that he was cooperating with the probes into both plots, but his lawyer declined to say whether he was working on a plea deal. Headley could face the death penalty if convicted of all 12 charges laid against him in Chicago. The US-born son of a former Pakistani diplomat and an American mother, Headley changed his name from Daood Gilani in 2006 so he could present himself in India as an American who was neither Muslim nor Pakistani, charging documents said. He allegedly told investigators he had been working with the group Lashkar-e-Taiba (LeT) since 2002. Indian media have reported that during five lengthy trips to Mumbai he befriended Bollywood stars while staying in an expat enclave near the US consulate. India and the United States signed an extradition treaty in 1997 to jointly combat militant groups and organised crime.