Noting that range and intensity of nuclear proliferation challenges is alarming, US Secretary of State, Ms Hillary Clinton on Thursday said the Obama administration is now engaged in diplomatic efforts to roll back this development, but supported the use of nuclear power for meeting the growing demand of energy world over.<br/><br/>In a major speech on nuclear non-proliferation she said the range and intensity of current nuclear proliferation challenges is alarming.<br/><br/>The international community failed to prevent North Korea from developing nuclear weapons. Iran continues to ignore resolutions from the United Nations Security Council demanding it suspend its enrichment activities and live up to those international obligations.<br/><br/>Ms Clinton said though thousands of nuclear weapons have been deactivated or destroyed, vast stocks of potentially dangerous nuclear materials remain vulnerable to theft or diversion.<br/><br/>She said that unless these trends are reversed soon, we will find ourselves in a world with a steadily growing number of nuclear-armed states and an increasing likelihood of terrorists getting their hands on nuclear weapons. <br/>