Within hours of the deadly Hamas attack on Israel that left hundreds of people dead, President Joe Biden was on the phone with Israeli Prime Minister Benjamin Netanyahu.

When Biden's counterpart -- reeling from one of the worst attacks on his country in decades -- brought up the possibility of going into Gaza, the president did not warn him against doing so, a US official briefed on the conversation tells CNN.

That decision by the president -- to hold back from urging Netanyahu to exercise restraint in the immediate aftermath of the attacks -- in no small part reflects the sheer shock and breadth of Hamas' brutal attack on Israel that makes this moment different, officials say.

And now, as Biden is poised to deliver his second speech to the nation since war broke out in Israel, the president and his national security team are keenly aware of what appears to be a growing likelihood of Israel making a ground incursion into Gaza.

Over the past 72 hours, officials have acknowledged what a deeply tenuous position that possibility puts the administration in. As a general matter, the US has historically urged for a ceasefire on all sides when conflicts have broken out in the region.

Further complicating the matter is the likelihood of American hostages being held inside Gaza.

In his phone calls with Netanyahu, Israel's response has been one of the points of discussion, though officials are being careful to share the degree to which Biden is offering his view on what the scale of Israel's response should be.

The Biden administration has always been very intent on handling those kinds of discussions very privately, and officials said this time will be no different.

Biden's first written statement over the weekend did not include the term "ceasefire" -- an omission that struck current and former administration officials alike.