Guterres wrote a letter to the president of the UN Security Council invoking Article 99 of the UN's charter, which states 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."

The humanitarian conditions amid the war in Gaza are "fast deteriorating into a catastrophe with potentially irreversible implications for Palestinians as a whole," Guterres said in the letter.

"Such an outcome must be avoided at all costs," he added.

It is the first time the UN chief has invoked the article since taking office in 2017.

The rotating presidency of the Security Council is currently held by Ecuador.

Urging the members of the Security Council to "press to avert a humanitarian catastrophe," Guterres reiterated his appeal for "a humanitarian ceasefire to be declared."

"The health care system in Gaza is collapsing," he said, adding that "there is no effective protection of civilians."

"The current conditions are making it impossible for meaningful humanitarian operations to be conducted," the letter said, adding that "nowhere is safe in Gaza."

The situation threatens "peace and security in the region," Guterres said.

"With a humanitarian ceasefire, the means of survival can be restored, and humanitarian assistance can be delivered in a safe and timely manner across the Gaza Strip."

In mid-November, after four rejected draft texts, the Security Council called for "extended humanitarian pauses" in the Gaza Strip, in what was the first time it broke its silence on the bloody conflict.

According to diplomatic sources, Security Council members are working on a new draft resolution focused on humanitarian aid.