The United Nations General Assembly has approved a resolution to begin work on a global treaty to control the trade in small arms.
Campaigners want to reduce the flow of arms to conflict zones
Only the United States voted against the plan, which calls on the UN chief to report within a year on the feasibility of such an accord.
Experts hope a treaty could control the flow of arms into conflict zones.
But the US argues that any global standard would be less restrictive than current US law.
UN spokesman Stephane Dujarric said that the non-binding resolution represented "the first formal step towards developing common international standards for the import, export and transfer of conventional weapons".
Under the resolution, incoming Secretary-General Ban Ki-moon was asked to seek members' views on the feasibility and scope of an agreement, and to establish an expert body to begin looking at a potential treaty in 2008.
Campaigners are seeking a treaty which would force countries to officially authorise all arms deals and prevent sales to governments likely to use the weapons to commit human rights abuses.
A group of 14 US senators had urged Secretary of State Condoleezza Rice to back the deal, arguing that a global standard was needed to complement regional and national initiatives.
But a US official said that America opposed the move "in order to maintain our higher standards".
Campaigners welcomed the vote, with Director of Oxfam International Jeremy Hobbs calling it a "historic step".
"Now governments must follow through and achieve a strong, effective treaty," the Associated Press news agency quoted him as saying.