Article 99 simply says that the Secretary-General "may bring to the attention of the Security Council any matter which in his opinion may threaten the maintenance of international peace and security.”

More specifically, this grants the UN Secretary-General the authority to bring to the attention of the Security Council any issue that may threaten international peace and security, even if it's not specifically on the agenda.

This article empowers the Secretary-General to inform the Security Council about situations or matters that might lead to conflict or tensions, allowing for proactive discussions and potential actions to address those issues.

A review of UN history shows that in the over 100 conflicts in which the Secretary-General intervened, only a very few included a formal Article 99 invocation. In addition to three explicit invocations recognized by the UN (Congo 1960, Iran 1979 and Lebanon 1989) there are over a dozen implied invocations in the Council.

Most of these, however, were late warnings or statements of support for warnings already provided by member states.

There have also been some warnings made at informal Council meetings but these are not direct invocations of Article 99, as interpreted by the UN, since the Secretary-General did not place a new item on the agenda of the Council or call for a special meeting.

Most significantly, in the vast majority of conflicts, no warning was given at all.

UN Spokesperson Stephane Dujarric described Article 99 as “the most powerful tool” at the UN chief’s disposal, adding that he expects Guterres to address the Security Council on Gaza this week and to press for a humanitarian cease-fire.

“One doesn’t invoke this article lightly,” Dujarric said, noting the article has not been used for decades.

“I think given the situation on the ground and the risk of complete collapse, not only of our humanitarian operations but of civil order, it’s something that he felt needed to be done now."

The decision comes as Israel pushes forward with its invasion of the Gaza Strip that has killed more than 17,700 people, most of them women and children, and displaced nearly 2 million from their homes.

In a letter to the Security Council's 15 members, Secretary-General Guterres echoed his plea for an urgent humanitarian ceasefire in the Gaza Strip, warning that Gaza’s humanitarian system was at risk of collapse after two months of war.

"We are facing a severe risk of collapse of the humanitarian system. The situation is fast deteriorating into a catastrophe with potentially irreversible implications for Palestinians as a whole and for peace and security in the region. Such an outcome must be avoided at all cost," the statement said.

It added that the conditions in the strip "are making it impossible for meaningful humanitarian operations to be conducted."