The United States signed a UN Arms Trade Treaty regulating the $70 billion global trade in conventional arms on Wednesday and the Obama administration sought to allay the fears of the powerful U.S. gun lobby which says the pact will violate the constitutional rights of Americans.

The treaty, which relates only to cross-border trade and aims to keep weapons out of the hands of human rights abusers and criminals, still requires ratification by the U.S. Senate and has been attacked by the influential gun rights group the National Rifle Association (NRA).

Among the NRA arguments against the treaty are that it undermines American sovereignty and that it disregards the Second Amendment of the U.S. Constitution, which guarantees citizens the right to bear arms.

The United States, the world's No. 1 arms exporter, became the 91st country to sign when U.S. Secretary of State John Kerry put pen to paper on the sidelines of the annual gathering of world leaders at the United Nations.

"This treaty will not diminish anyone's freedom, in fact the treaty recognizes the freedom of both individuals and states to obtain, possess and use arms for legitimate purposes," Kerry said after signing the treaty.

"Make no mistake, we would never think about supporting a treaty that is inconsistent with the rights of Americans, the rights of American citizens to be able to exercise their guaranteed rights under our constitution," he said.

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 (ATT) 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.

"This treaty threatens individual firearm ownership with an invasive registration scheme," said Chris Cox, executive director of the NRA's Institute for Legislative Action, in a statement. "The NRA will continue working with the United States Senate to oppose ratification of the ATT."

"These are blatant attacks on the constitutional rights and liberties of every law-abiding American. The NRA will continue to fight this assault on our fundamental freedom," he said.

Unscrupulous trade

The UN Office for Disarmament Affairs says the treaty does not "interfere with the domestic arms trade and the way a country regulates civilian possession."

The 193-nation UN General Assembly overwhelmingly approved the treaty on April 2. Russia, China, India and 20 other countries abstained in the April 2 vote. The treaty will enter into force 90 days after 50 nations have ratified it. So far five countries have ratified the treaty.

Rights group Amnesty International USA said it hoped the decision by the United States to sign the treaty would send a signal to Moscow, Beijing and the NRA on the commitment of President Barack Obama's administration to the issue.

"The Obama administration is politically committed to ending the unscrupulous trade in deadly weapons used by dictators, war lords and criminal gangs to commit atrocities," said Amnesty International USA deputy executive director Frank Jannuzi.

Aid group Oxfam welcomed the U.S. signing and called on Washington to live up to the spirit of the treaty by not transferring weapons to countries where there is a risk of rights abuses, such as in the Syrian civil war.

The White House pledged in June to provide military aid to rebels in Syria. The Syrian Coalition of opposition groups said this month that lethal assistance had been received from the United States. Kerry has said "many items" are reaching the rebels but declined to say what military items were sent.

Kerry said on Wednesday the Arms Trade Treaty requires other countries to create and enforce strict national arms export controls that the United States already has in place.

"We are talking about the kind of export controls that for decades have not diminished one iota our ability in the United States as Americans to exercise our rights under the constitution," he said.