From the Wikipedia article above (with references):
It is thought that between 17 and 20 states have weapons incorporating depleted uranium in their arsenals. They include the USA, the UK, France, Russia, Greece, Turkey, Israel, Saudi Arabia, Bahrain, Egypt, Kuwait, Pakistan, Thailand, Iraq and Taiwan. DU ammunition is manufactured in 18 countries. Only the US and the UK have acknowledged using DU weapons.<3>
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There is no specific treaty ban on the use of DU projectiles. There is a developing scientific debate and concern expressed regarding the impact of the use of such projectiles and it is possible that, in future, there will be a consensus view in international legal circles that use of such projectiles violate general principles of the law applicable to use of weapons in armed conflict. No such consensus exists at present.