Does a man's fondling of his wife during the daytime in Ramadan invalidate his fast?

A fasting person is permitted to fondle and kiss his wife if he controls himself and is confident that his fast will not be invalidated. This is because the Prophet used to do so. However, if one fears falling into the prohibited, then it becomes disliked for him to do so. If semen is ejaculated, one must then abstain from eating and make up for that day, but there is no expiation required. As for pre-seminal fluid (madhy), it does not invalidate the fast.