BRUSSELS, Feb 19 (Reuters) - The European Union on Monday warned Israel against launching an offensive in Rafah that ministers said would create a disaster for the roughly 1.5 million refugees crammed into the city on the southern edge of Gaza. “An attack on Rafah would be absolutely catastrophic … it would be unconscionable,” Ireland’s Foreign Minister Micheal Martin said before a meeting with foreign ministers from the 27 EU member states in Brussels.