GENEVA (Reuters) - A deadlock in global negotiations on fissile material has increased the risk that nuclear weapons could spread or fall into the hands of violent political groups, the head of the United Nations warned Wednesday. Addressing the Conference on Disarmament, which has been unable to launch negotiations on any issue for more than a decade, UN Secretary-General Ban Ki-moon said the impasse had ominous implications for international security. The longer it persists, the graver the nuclear threat from existing arsenals, from the proliferation of such weapons and from their possible acquisition by terrorists, Ban told the United Nations-sponsored forum. Halting production of bomb-making fissile material is widely seen as the next step in multilateral nuclear arms control. But for the past year, Pakistan has blocked consensus to launch talks to halt production of plutonium and highly-enriched uranium. It insists that existing fissile stocks should also be included, to counter Indias perceived strategic advantage. One or two members should not be able to block indefinitely the required consensus at the 65-member forum, Ban stressed. Pakistans ambassador Zamir Akram said Tuesday that US moves to support Indian membership in four key multilateral export control regimes that allow trade in nuclear materials had boosted Islamabads opposition to fissile talks. The United States says that in line with President Barack Obamas nuclear agenda laid out in Prague in 2009, to eventually rid the world of nuclear arms, a fissile material cut-off treaty is at the top of its very ambitious 'to do list. Washingtons preference is to launch full-fledged fissile negotiations as part of a program of work requiring formal adoption, but it could agree to a robust discussion in the meantime, US disarmament ambassador Laura Kennedy says. Were realistic about the way ahead, but committed, she told a briefing last week. The Conferences members include all five official nuclear powers (Britain, China, France, Russia and the United States), nuclear-armed India and Pakistan, and Israel, widely assumed to have atomic weapons. Iran and North Korea, both under sanctions for their nuclear programs, are also members. As the worlds sole disarmament negotiating forum, the CD risks losing all credibility unless it engages in serious discussions, Ban said: Continued inaction will only endanger its future as a multilateral negotiating forum, he warned. The future of the CD is in your hands. The forum has been unable to gain traction despite other recent advances in arms control, including the New START treaty clinched by the United States and Russia last April, he said. Earlier Tuesday, Russias parliament ratified the pact which the US Senate approved last month. It commits the countries to ceilings of 1,550 deployed strategic warheads in seven years.