The US government's plans to give every state a veto over a crucial arms trade treaty must be rejected by the British government, Oxfam and Amnesty International UK have said.
The Arms Trade Treaty (ATT) is under discussion this month at the United Nations in New York.
The British government is leading multilateral efforts to secure a resolution that will kick- start official UN negotiations on the ATT next year.
Amnesty International UK and Oxfam warn that efforts to secure an effective treaty could be derailed by the US government's demands for a clause to be inserted which would give any government the power of veto during the proposed UN negotiating conference.
The two agencies add that it could also bring negotiations to a grinding halt.
"The British government has so far been a leading voice for a robust arms trade deal and much of this is down to the personal commitment of [the UK Foreign Secretary] David Miliband. The UK must not support the veto option, as it would jeopardise the prospects for a treaty it promoted so passionately on the international stage", said Debbie Hillier of Oxfam International.
Amnesty International UK Campaigns Director, Tim Hancock, said: "Lax controls on the arms trade have led to serious human rights violations being committed in many parts of the world, causing untold suffering. It is absolutely essential that a robust international Arms Trade Treaty is established. This is not the time for concession."
Over the past fortnight, Oxfam and Amnesty International published two reports saying that armed violence costs around 2,000 lives every single day and irresponsible arms transfers are creating human rights crises affecting millions more.
They called on governments meeting in New York this month to agree to start negotiations for a robust treaty which would control the flow of weapons and ammunition and prevent arms deals that fuel poverty, conflict, armed crime and abuse of human rights.