UNITED NATIONS (Reuters) – Three dozen arms control and human rights groups have written to US President Barack Obama ahead of new arms-trade negotiations at the United Nations next month, urging him to back a tough treaty that would end loopholes in international weapons sales. Arms control campaigners say one person every minute dies worldwide as a result of armed violence and a convention is needed to prevent the unregulated and illicit flow of weapons into conflict zones and fueling wars and atrocities. The UN General Assembly voted in December to restart negotiations in mid-March on what could become the first international treaty to regulate the $70 billion global arms trade after a drafting conference in July collapsed because the United States and other nations wanted more time.