Israel-Gaza-Lebanon live updates: Some UN members walk out as Netanyahu speaks

A senior official in President Joe Biden's administration told ABC News the U.S. cannot rule out the possibility of an Israeli invasion into Lebanon following the escalation of its airstrike campaign on Monday.

"I think it is important for everyone to take Israeli preparations seriously," the senior administration official said.

The U.S. is putting its hope in engagements on the sideline of the United Nations General Assembly this week, said the senior administration official, who expressed hope that the informal meetings could lead to "illusive solutions" or "at least make some progress" toward resolving the crisis in the Middle East.

The official said Secretary of State Antony Blinken would discuss "the increasing challenges" across the so-called "Blue Line" dividing Israel and Lebanon at a meeting with his G7 counterparts.

At that engagement and through the week, the a key U.S. focus will be "finding an off ramp," they said.

"We've got some concrete ideas with allies and partners we are going to be discussing," the official added.

-ABC News' Shannon Kingston

A U.S. official tells ABC News that the "small number of additional U.S. military personnel being sent to the Middle East," announced this morning by the Pentagon is a small special operations team that will work in planning for a non-combatant evacuation operation should itbe needed.

-ABC News' Luis Martinez

A Lebanese parliament member addressed the United Nations General Assembly Monday sharing a warning that the country's citizens are in danger as tensions between Israeli forces and Hezbollah intensify.

Member Bahia El Hariri attended the U.N. meeting in place of Lebanon's Prime Minister Najib Mikati.

"The people of Lebanon are in serious danger after the destruction of large areas of agricultural land and the targeting of residential buildings in the majority of the regions of Lebanon," Hariri said.

"This has damaged the economy of our country and threatened our social order, especially since several countries have asked their nationals to leave our country," she added.

Separately, U.N. Secretary-General António Guterres said he was "gravely alarmed" by the escalating situation between northern Israel and southern Lebanon and the "large number of civilian casualties, including children and women, being reported by Lebanese authorities, as well as thousands of displaced persons, amidst the most intense Israeli bombing campaign since last October," in a statement issued by his spokesperson Monday.

"The Secretary-General is also gravely alarmed" by the continued Hezbollah strikes on Israel, the statement added.

-ABC News' Ellie Kaufman

Israeli Air Force fighter jets attacked "1,600 terrorist targets of Hezbollah" in parts of southern Lebanon in "several attack waves," on Monday, the IDF said in a post on X.

-ABC News' Ellie Kaufman