US Secretary of State John Kerry signed the arms trade treaty on Wednesday at the United Nations in New York, making the United States the 91st country to agree to the measure.

Kerry called the treaty a "significant step" in preventing terrorists from obtaining conventional weapons.

Despite the sign of support from the administration of US President Barack Obama, the treaty does not take effect until 50 nations have ratified it. In the US Congress, this is not a foregone conclusion as many lawmakers have expressed doubts.

In a letter to Obama on Tuesday, Senator Bob Corker – the leading Republican on the Senate Foreign Relations Committee – said there were still "significant legislative and constitutional questions."

Among them is the concern that the treaty could conflict with the Second Amendment of the US Constitution, which guarantees citizens the right to bear arms.

The treaty will subject trade in conventional weapons, from guns to tanks, to strict rules. It prohibits the export of weapons if such trade violates arms embargoes or if the weapons could be used in genocide, crimes against humanity, by violent extremists or organized crime gangs. It calls for the establishment of national control systems to regulate the import and export of conventional arms, ammunition and weapon parts. It also controls arms dealers. The treaty does not regulate the use of arms domestically.

Kerry addressed the concerns of some American lawmakers, saying the US "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."

Italy on Wednesday became the first European Union country – and fifth UN member overall – to actually ratify the treaty. Italy is the world's eighth largest arms exporter, while the US is the largest.

mz/lw (AFP, Reuters)