Israel-Gaza-Lebanon updates: IDF orders evacuations in Beirut as huge blast hits city

Senior Hamas leader Yahya Sinwar, one of the key architects of the Oct. 7 attacks on Israel, has gone radio silent, according to an official familiar with negotiations to reach a cease-fire and hostage release deal.

Sinwar's absence has created another hurdle for U.S. officials who are still trying to complete an overdue "final" proposal for a deal.

It has also sparked speculation that Sinwar is dead, but the official said there is no indication that's the case.

State Department spokesperson Matt Miller spoke about Hamas' role in delaying a cease-fire proposal during a briefing Monday, but did not weigh in on Sinwar's status specifically.

"When it comes to Sinwar, I don't have any update on his condition at all, one way or the other," he said, before asserting that Hamas has been unwilling to "engage at all" with Egyptian or Qatari mediators "over the past several weeks."

"So the reason you have not seen us put forward this proposal is we can't get a clear answer from Hamas of what they're willing to entertain and what they're not willing to entertain," he said. "We're going to continue to try to work it."

-ABC News' Shannon Kingston

Israel's limited ground incursion into Lebanon could be imminent, two more U.S. officials have told ABC News.

One of the officials said Israel notified the U.S. of its intentions.

Deputy Pentagon press secretary Sabrina Singh would not confirm as much when repeatedly asked Monday, but did give new details on the additional forces being sent to the region to potentially defend Israel and its own forces.

"These augmented forces include F-16, F-15E, A-10, F 22 fighter aircraft and associated personnel," Singh said.

The fighter aircraft are to be used for air defense, such as intercepting missiles if needed, according to Singh. There are "an additional few thousand" troops in the region as part of the augmented force, according to Singh.

-ABC News' Luis Martinez and Matt Seyler

The U.S. expects Israel to imminently begin a limited ground operation into Lebanon that would be targeted, in order to clear out Hezbollah infrastructure near Israeli border communities and then pull their forces back, according to a senior U.S. official.

This could start "immediately," according to the senior official.

-ABC News' Selina Wang

Speaking to reporters Monday at the White House, President Joe Biden addressed Israel's continued attacks on Lebanon and reports that they are preparing for a limited ground operation.

The comment, which followed Biden’s remarks on Hurricane Helene, came after a reporter asked if he was aware of and "comfortable" with the possibility of Israel invading Lebanon.

"I'm more aware than you might know, and I'm comfortable with them stopping. We should have a cease-fire now," Biden replied.