Speaking to reporters at the UN headquarters in New York, Guterres said the Middle East "is a powder keg with many parties holding the match," Xinhua reported.
"I have warned for months of the risks of the conflict spreading," said the UN chief, adding that the situation in the occupied West Bank is "boiling over," and attacks in Lebanon are threatening the entire region.
He said that over the last few days, exchanges of fire between Hezbollah and the Zionist regime have intensified across the Blue Line, in total disregard of Security Council resolutions 1701 and 1559.
Guterres noted that large-scale Israeli strikes deep into Lebanon, including Beirut, have killed more than 2,000 people over the last year -- and 1,500 in just the past two weeks alone.
"We are on the verge of an all-out war in Lebanon, with already devastating consequences. But there is still time to stop," he said.
"The sovereignty and territorial integrity of all countries must be respected," he stressed.
The secretary-general commended the UN peacekeeping force in Lebanon, known as UNIFIL, for continuing "to carry out their mandates to the extent possible," and called on all actors to ensure their safety and security.
AMK/PR