NEW YORK - A new report by the Federation of American Scientists (FAS) claims that Pakistans fast-growing nuclear weapons arsenal is at greater risk due to the emergence of powerful militant groups with links to the countrys security services, a claim disputed by a US expert. Even the reports author, Charles Blair, who is director of FASs Terrorism Analysis Project, said that he believes Pakistan can still keep its nuclear assets safe. 'My conclusion isnt that Pakistan is likely to lose control of fissile material, he told The Wall Street Journal. 'But the threat is obviously growing, he added. George Perkovich, an expert on Pakistans nuclear programme at the Carnegie Endowment for International Peace in Washington, was quoted as saying in media reports that it is incorrect to draw conclusions that because militants have been able to attack Armed Forces installations, some perhaps with insider help from Islamist-leaning military officers, than nuclear weapons also could be at risk. 'Pakistans nuclear weapons are the safest, most secure things in Pakistan, he said. 'Theyre more motivated to keep nuclear weapons in their control than anything else, he stated. The report, entitled 'Anatomizing Non-State Threats to Pakistans Nuclear Infrastructure: The Pakistani Neo-Taliban, was released on Wednesday by the Federation, which was set up in 1945 by many of the scientists who built the first atomic bombs and were worried about dissemination of the technology. The Wall Street Journal said the report is likely to make waves in the US and India , where public opinion towards Pakistan is increasingly hostile in the wake of the secret US raid in Abbottabad which killed Osama bin Laden in his hideout. The report was supposed to be brought out at the end of the year but in an introductory section FAS said it decided to move the release forward because of Osama bin Ladens killing and 'ongoing concerns about Pakistans links to Jihadist organisations targeting the US and its interests. But the report includes no new information on why Pakistans nuclear assets are at heightened risk beyond saying militants have been able to mount successful attacks on Armed Forces installations in the past few years, including an attack on a naval base in Karachi.