It is coercion to break the fast under threat of death for the sick or the traveler; as narrated by Ibn Abbas from the Prophet (peace be upon him) who said: ((Indeed, Allah has excused my nation from mistakes and forgetfulness and what they are coerced to do)), in Sunan Ibn Majah 29:5, and Sahih Ibn Hibban 87:11, thus it is obligatory for him to break the fast, and he cannot refrain from doing so; if he does, he will be sinful.