India today said that the nexus between terror groups and official stablishment in Pakistan is getting stronger which makes it difficult to deal with the menace of terrorism. Speaking at a seminar in New Delhi today, the National Security Advisor, Mr. Shivshankar Menon said that the interrogation of David Coleman Headley, key accused in the Mumbai terror attack has revealed clear links of the terror groups with the official establishment and intelligence agencies of Pakistan. He said unfortunately this nexus cannot be broken soon. Mr. Menon's comments come days after the Home Secretary, Mr. G.K. Pillai said that the ISI played a major role in the Mumbai attack and it was literally controlling and coordinating the attacks from the beginning till the end. According to official sources, Headley also corroborated the statement of lone captured terrorist, Ajmal Amir Kasab that the terrorists got training from Pakistan Navy during his interrogation by the Indian officials in the US. Mr. Menon said that India has a much clearer picture of terror infrastructure and its support system in South Asia. He said that the terror groups in the region have fused together in such a way that the traditional distinctions between them have become meaningless. Expressing concern over reports of acquisition of nuclear weapons by terror groups, he stressed on the need to develop better instruments to counter the threat of terror.