"The parties must urgently recommit to the full implementation of Security Council resolution 1701 and immediately return to a cessation of hostilities," Guterres told journalists.
UN peacekeepers are also on the ground trying to de-escalate the tense situation, he added.
"Let’s be clear: The people of the region and the people of the world cannot afford Lebanon to become another Gaza," Guterres noted.
Israel and Hezbollah have exchanged fire almost daily since the October 7 Hamas attack on Israel and the Israeli assault on Gaza.
On Tuesday, the Israel Defense Forces said it had approved and validated operational plans for an offensive in Lebanon as part of a situational assessment. Israeli Foreign Minister Israel Katz said later that Israel was very close to reaching a decision to "change the rules" against Hezbollah. Katz warned that an all-out war will destroy Hezbollah and severely hit Lebanon.