UN Secretary-General Antonio Guterres warned the Security Council on Wednesday that "the war between Israel and Hamas fighters in the Gaza Strip could exacerbate existing threats to international peace and security." Guterres relied on Article 99 of the UN Charter, which is rarely used, allowing him to "bring to the attention of the Security Council any matter he deems may threaten the protection of international peace and security." In a letter to the 15 member states of the council, Guterres wrote, "We face a grave risk of a collapse of the humanitarian system. The situation is rapidly deteriorating into a disaster with potentially irreversible effects on Palestinians as a whole and on peace and security in the region." He added, "Such an outcome must be avoided at all costs."