לזכות משה יהודה בן פעשא דינה
The Rambam writes in a letter that one who denies tchiyas hemeisim is a kofer because if he denies tchiyas hameisim that will lead him to deny Hashem's wonders in this world which IS actual kfira.
Odd, pointed out Rav Hutner [Igros 40], that one should be considered a kofer for a belief that is itself not kfira but will lead to kfira. Where do we find that one is a kofer for harboring a belief that is not kfira but will lead to kfira??
I saw a terutz in a sefer which I won't share because I don't think it is correct. I am waiting for someone to solve this problem.