Is it permissible for a Muslim to be a sincere friend to a non-Muslim?

A Muslim is not permitted to befriend a polytheist (mushrik) or take him as an intimate friend, because Islam calls for shunning disbelievers and disavowing them, as Allah Almighty says: "O you who have believed, do not take as allies a people with whom Allah has become angry." And the Prophet, peace and blessings be upon him, guided to this, saying: "Do not accompany anyone but a believer, and let no one eat your food except a pious person," and his saying: "Do not dwell with the polytheists and do not associate with them; whoever dwells with them or associates with them is not of us." Nevertheless, it is permissible to treat them kindly in hopes of their embracing Islam, as the Prophet, peace and blessings be upon him, did with the Jewish boy who served him.