I would like to ask if belief in God is compulsory in Judaism?

I would like to ask if belief in G-d is compulsory or not in Judaism.Rabbi Marc Alain Ouaknin says that belief in G-d is not mandatory in Judaism.One is bound to perform the mitzvot(even if he does so only for identity,heritage and cultural reasons);but belief in G-d is not compulsory.Is this true?