NIAMEY, July 29 (Reuters) - The European Union and France have cut off financial support to Niger and the United States has threatened to do the same, after military leaders this week announced they had overthrown the democratically elected president, Mohamed Bazoum. Niger's foreign allies so far have refused to recognize the new military government led by General Abdourahamane Tiani, previously head of the presidential guard, who officers declared head of state on Friday. The Economic Community of West African States (ECOWAS), and the West African Monetary Union will hold emergency summits in Nigeria on Sunday to discuss the situation, and further economic and financial sanctions could be decided