Decision to secure an admission or Wait out for better offers

[Srividhya]

I received full funding for my Masters with the Ph.D. program at ISAE France (Renowned European University for Aerospace, few might be familiar). But I am waiting for my Ph.D. Application results from Ivy League schools and some top schools in the USA. I am supposed to send my decision within few days to ISAE with a down payment. But I can't make an informed decision without knowing the results of other US schools. IShould I wait for the US Universities results with confidence or secure this admission as a backup option by making the payment? For the record, I have good GPA, 4 Research experiences, 3 Publications, and some other accomplishments. Overall a decent profile for any Ivy League school. If anyone got any suggestions, please post your comments regarding this. Help!!!!!!!!!