* More than 60 nations sign treaty, 50 ratifications needed
* One person dies each minute from armed violence -activists
* NRA vows to oppose U.S. Senate ratification (Adds figure for expected signatures, British minister)
By Louis Charbonneau
UNITED NATIONS, June 3 (Reuters) - Delegates from dozens of countries gathered in New York on Monday and signed the first treaty to regulate the $70 billion global conventional arms trade, but the United States was not among them.
On April 2, the 193-nation U.N. General Assembly overwhelmingly approved the U.N. Arms Trade Treaty that aims to keep weapons out of the hands of human rights abusers and criminals.
Argentina's foreign minister, Hector Timerman, was the first to put pen to paper when the signing ceremony opened at U.N. headquarters on Monday. There was a large round of applause after he affixed his signature to the document.
The United Nations said 62 countries from Europe, Latin America, Asia and Africa signed the treaty in the morning. German Foreign Minister Guido Westerwelle was due to sign shortly, making Germany the 63rd nation to join the pact.
U.N. High Representative for Disarmament Affairs Angela Kane told reporters that several more states would likely be signing in the coming days, taking the initial tally to roughly 66.
The United States, the world's No. 1 arms exporter, will sign the treaty as soon as all the official U.N. translations of the document are completed, U.S. Secretary of State John Kerry said in a statement.
"The signing of the Arms Trade Treaty gives hope to the millions affected by armed violence every day," said Anna Macdonald of the humanitarian group Oxfam. "The devastating humanitarian consequences of the ... conflict in Syria underline just how urgently regulation of the arms trade is needed."
"Gunrunners and dictators have been sent a clear message that their time of easy access to weapons is up," she added. "For generations the arms trade has been shrouded in secrecy but from now on it will be open to scrutiny."
Arms control activists and rights groups say one person dies every minute as a result of armed violence and the treaty is needed to halt the uncontrolled flow of arms and ammunition that they say fuels wars, atrocities and rights abuses.
The Arms Trade Treaty aims to set standards for all cross-border transfers of conventional weapons ranging from small firearms to tanks and attack helicopters. It would create binding requirements for states to review cross-border contracts to ensure that weapons will not be used in human rights abuses, terrorism, violations of humanitarian law or organized crime.
IRAN, SYRIA, NORTH KOREA OPPOSED TREATY
Iran, Syria and North Korea cast the only votes against the treaty in April. The same three states had prevented a treaty-drafting conference at the U.N. headquarters in March from reaching the required consensus to adopt the pact.
The treaty will enter into force 90 days after 50 nations have ratified it. Finnish Foreign Minister Erkki Tuomioja said the treaty could come into force in "slightly more than a year" depending on how quickly national ratifications come.
The National Rifle Association, a powerful U.S. pro-gun lobbying group that opposed the treaty from the start, criticized the U.S. delegation in April for being among the 154 U.N. member states that voted in favor of the pact.
The NRA has vowed to fight to prevent the treaty's ratification by the U.S. Senate when it reaches Washington. The group says the treaty will erode citizens' right to bear arms, an interpretation the U.S. government disputes.
The treaty "will not undermine the legitimate international trade in conventional weapons, interfere with national sovereignty, or infringe on the rights of American citizens," Kerry said in his statement.
Alistair Burt, under secretary of state at the British Foreign Office, urged countries to move swiftly with the ratification of the treaty.
"The world has already waited too long and we should not and will not lose the momentum gained," he said after signing. "Our goal is early entry into force and universal application."
Russia, China, India and 20 other countries abstained in the April 2 vote. Many nations that abstained criticized the treaty as discriminatory. U.N. diplomats say the treaty's effectiveness could be limited if major arms exporters and importers refused to sign it. (Editing by Mohammad Zargham)