Britain is to push for ammunition sales to be covered by new international arms trade controls despite strong resistance from the US.
The UK sees the inclusion of ammunition as an essential element of the proposed Arms Trade Treaty and will negotiate hard for it when a month-long conference opens at the United Nations in New York next week.
But the British delegation faces opposition from a number of countries including China, Egypt and Syria but also its traditional ally America.
Russia, which has faced condemnation for selling arms to President Bashar Assad's regime in Syria, is also unlikely to sign a treaty that will prevent it from doing so in future.
Failure to bring sceptics on board will mean that the treaty either has to be watered down or will have less international reach.
Six years in gestation, the treaty is intended to establish common international standards on the trade in arms and prevent illicit sales.
Signatories will have to control arms exports and block those that might, for example, support human rights abuses, conflict and corruption.
However, the precise coverage of the treaty will be thrashed out at the July conference and compromises are inevitable.
The UK wants the agreement to regulate the sale of all conventional weaponry, small arms, light weapons, parts and components, ammunition and military technology. Ammunition is seen as fundamental, as without it weapons cannot be used.
Britain's negotiators are keen to avoid a weak treaty which they cannot sign up to but also want to ensure that it is widely supported.