US President Joe Biden asked world leaders Tuesday to prevent "full-scale war" over Lebanon, as clashes escalated between Israel and Hezbollah, prompting the UN chief to warn of a situation "on the brink."

The UN General Assembly, the high point of the diplomatic calendar, comes as Lebanese authorities say Israeli strikes killed 558 people -- 50 of them children.

"Full-scale war is not in anyone's interest. Even though the situation has escalated, a diplomatic solution is still possible," Biden said in his farewell address to the global body.

"In fact (it) remains the only path to lasting security to allow the residents from both countries to return to their homes on the border safely," Biden said.

Biden also pushed again for an elusive ceasefire between Israel and Hamas, telling the global body it was time to "end this war."

UN Security Council member France called for an emergency meeting on the crisis, as the EU's top diplomat Josep Borrell warned "we are almost in a full-fledged war."

"We should all be alarmed by the escalation. Lebanon is at the brink," UN Secretary-General Antonio Guterres said.

President Masoud Pezeshkian of Iran -- which backs both Hezbollah and Hamas -- condemned the "senseless and incomprehensible" inaction by the UN against Israel.

The United States, Israel's closest ally, has opposed a ground invasion into Lebanon. A senior official said ahead of Biden's speech that the United States would bring "concrete" ideas for de-escalation to the UN.

It is unclear what progress can be made to defuse the situation in Lebanon as the efforts to broker a ceasefire in Gaza, which Israel has relentlessly pounded since October 2023, have come to nothing.

Guterres cautioned against "the possibility of transforming Lebanon (into) another Gaza," calling the situation in the embattled Palestinian territory a "non-stop nightmare."