Prime Minister David Cameron has welcomed a landmark deal regulating the international arms trade, saying it will "ease the immense human suffering" caused by conflicts.
The United Nations General Assembly resolution backing the arms trade treaty was overwhelmingly passed by a vote of 154 to three, with 23 abstentions.
Iran, North Korea and Syria were the only nations in the 193-member body to vote against the treaty.
Mr Cameron said: "This is a landmark agreement that will save lives and ease the immense human suffering caused by armed conflict around the world. It will reduce the number of illegal arms and make it harder for these to reach the hands of criminals and terrorists who are set on using them to destroy the lives of others.
"We should be proud of the role Britain has played to secure this ambitious agreement, working with international partners to secure this momentous step that will make our world safer for all."
The treaty will not control the domestic use of weapons in any country, but it will require countries to establish national regulations to control arms transfers. The document covers battle tanks, armoured combat vehicles, large-calibre artillery systems, combat aircraft, attack helicopters, warships, missiles and missile launchers, small arms and light weapons.
Deputy Prime Minister Nick Clegg said he hoped that the treaty could be strengthened and expanded in future.
He said: "This treaty will bring much greater - and much needed - regulation to arms sales across the world and is a big step forward in clamping down on weapons going to rogue regimes and to the black market. It will save lives and help to combat terrorism."
Shadow foreign secretary Douglas Alexander said: "I strongly welcome the adoption of the arms trade treaty by the UN General Assembly. The treaty will significantly boost efforts to stem the flow of arms to some of the world's most volatile places, and will help end the transfer of weapons used to commit genocide, crimes against humanity and war crimes.
"The UK Government now has an opportunity to show international leadership, and ensure a progressive interpretation of the treaty and its measures."