Happening now breaking news as Israel remains on very high alert

US officials say they believe Iran has not yet decided exactly how to follow

through on its threat of retaliation for the

killing of a Hamas leader in Tehran also breaking. President Biden says he's

concerned, his word concerned about the prospects for a Gaza cease fire deal as Iran's threat

to attack Israel looms.

The United States dispatching key officials here to the Middle East just ahead of very high stakes negotiations on Thursday.

Welcome to our viewers in the United States and around the world.

I'm Wolf Plitzer in Tel Aviv and you're in the situation room. This is CNN breaking news.

We begin with the breaking news.

President Biden speaking publicly about the threat of an Iranian attack on Israel as

U.S. officials are sharing their insights into why Tehran has not

yet moved ahead with a retaliatory strike.

CNN's Nick Robertson is with me here in Tel Aviv but first let's go to see an as

m j. m j. m j. what are you hearing from US officials and from the

president himself well wolf this ceasefire deal that has been elusive for so many months

clearly became even more complicated after the death of Hamas leader

Ismail Hania in Tehran. President Biden, who remember, until quite recently, had expressed real

optimism about these talks, just told reporters in New Orleans that these talks had in fact

become more difficult.

Take a listen.

If you can still get to a ceasefire dealer,

...