The White House says President Biden# against the Iran-backed militia that killed# three American soldiers in Jordan yesterday.

From Yemen, to Iraq, to Syria,## and now Jordan, American forces are en Nick Schifrin starts our coverage.

NICK SCHIFRIN: It is in a remote desert# corner at the and the attack on Tower 22 today# led to a U.S. vow of revenge.

LLOYD AUSTIN, U.S. Secretary of Defense: The# president and I will not tolerate attack on## U.S. forces, and we will take all necessary# actions to defend the U. ANTONY BLINKEN, U.S. Secretary of State: We# will respond decisively to any aggression,## and we will hold responsible the# people who attacked our troops.

NICK SCHIFRIN: U.S. military and defense# officials say an Iranian-backed mi fired a single explosive drone that# landed in soldiers' barracks and go through the base's air defense because# it was misidentified as a U.S. drone.

The three soldiers killed were U.S. Army Reservist# Sergeant William Rivers, Specialist Kennedy## Sanders, and Specialist Breonna Moffett.

Bases# in Iraq and Syria have been targeted repeatedly## since mid-October, but this weekend's was# the first in Jordan.

Tower 22 is located on## the Jordan side of a remote demilitarized# zone where Jordan, Iraq and Syria meet.

To the north is the U.S. Al-Tanf garrison in# Syria.

It relies on Tower 22 for logistics## and other support.

For years, Al-Tanf has# functioned as a launching point for special## forces combating ISIS militants and monitors a# weapon shipping route along a highway leading## into Baghdad.

The base has been the target of# previous strikes by Iranian-backed militias.

It's also right next to the vast# Rukban refugee camp.

At its peak,## more than 100,000 internally displaced Syrians# were crowded there, seeking refuge from ISIS but blocked by Jordan from crossing the border.

JOHN KIRBY, NSC Coordinator For Strategic# Communicatio war.

We do not see NICK SCHIFRIN: At the White House today,# na said the U.S. will respond in a way that does# not escala JOHN KIRBY: We will do that on our schedule# in our time, and we will do it in the manner## of the president's choosing as commander in# chief.

We will also do it fully cognizant of## the fact that these groups, backed by Tehran,# have just taken the lives of American troops.

NICK SCHIFRIN: Iran's Foreign Ministry# today said militia groups act on their own.

NASSER KANAANI, Iranian Foreign Ministry Spokesman# (through translator): The Islamic Republic of## Iran does not interfere in the decisions of# the resistance groups on Palestinian nation or defend themselves and their# people against any aggression and occupation.

GEOFF BENNETT: And Nick Schifrin joins us now.

So, Nick, what is th NICK SCHIFRIN: U.S. officials obviously# won't telegraph the punch, as they put it.

But, until this weekend, they have# been very selective.

In Iraq and Syria,## they have responded to the 150-plus attacks# before this weekend by going after things like## weapons storage facilities, missiles, drones,# factories.

They have tried to calibrate it,## so they don't actually kill members of the# militia, so as, in their words, not to escalate.

Same in Yemen.

The targets over about 10# rounds of U.S. and U.K. strikes have again## been missiles and drones that the Houthis have# been using to fire at ships and not trying to## attack Houthi command-and-control# with senior Houthi leadership.

But this is a different size of attack,# as you said and as the package said,## and the U.S. response is likely to be larger.# And there are critics of the administration o today saying it must be much larger.# We heard from Senator Roger Wicker,## the ranking member in the Senate# Armed Services Committee.

He wants## to see a strike directly at -- quote --# "Iranian targets" and its Mi ke Rogers, the chairman of the House# Armed Services Committee, Republican,## criticized President Biden, saying his fear# of escalation has morphed into doctrine of## appeasement.

So there is this argument that# says the administration must go a lot farther,## but the administration officials I talk to# say exactly you heard just John Kirby say:## Look, we do not want this to turn# into a regional war.

Therefore,## we will continue to try and calibrate our# response so it doesn't escalate fu GEOFF BENNETT: On another matter,# Nick, we know that the CIA director,## Bill Burns, met over the weekend with# his Israeli in a meeting that was mediated by# Qatar.

What came of that meeting?

They were talking about a hostage deal.

NICK SCHIFRIN: Right, right.

at least temporarily.

And that group# that you just laid out has been an## effective one.

They're the ones who brought# about the November cease-fire the release of more than 100 hostages.

These# are four men who have met many times before.

There you see Bill Burns on the left, the# Qatari prime minister, and the Israeli and## Egyptian intelligence chiefs.

Now -- and they# believe that they have made progress.

And the## progress is that they have an outline that they# believe Israel accepts that would allow for the## release of women and children, and in exchange# for a certain amount of time for a cease-fire.

Officials won't give the exact details.

And# then that round would essentially lead to a## second round of more releases.

And then the final# round would be Israeli soldiers and dead bodies.

And, again, what U.S. officials hope is# that, if they can make progress on that deal,## which is a temporary cease-fire for the# release of hostages as well as the release## of Palestinians detained in Israel, that# could lead to a more permanent cease-fire## and what the U.S. is really hoping for, progress# across the region, namely, normalization between## Israel and Saudi Arabia and steps toward# a two-state solution for the Palestinians.

GEOFF BENNETT: So, more to come on that front.

Meantime, the U.N. agency th by Hamas.

As I understand it, Israel has# created a dossier about that.

What does it say?

NICK SCHIFRIN: Yes, the dossier was attained## by "PBS NewsHour," It says that 13 UNRWA staffers in total# were involved in October the 7th.

And## you see there four UNRWA staff were# involved in kidnapping on October the## 7th.

Six UNRWA staff infiltrated into# Israel.

It also says Hamas fighters## have used UNRWA facilities as hideouts to# conceal weapons within UNRWA equipment.

And there's also longer-term collaboration# between UNRWA and Hamas in this dossier.## Hamas built tunnels under the headquarters# of UNRWA, under an UNRWA school, and that,## in total, 10 percent of all of UNRWA is# actually Hamas and Palestinian Islamic Jihad,## an other militant group.

That# is about 1,200 of 13,000 people.

But here's the problem.

UNRWA is the only game# in town when it comes to deliveri aid.

The U.S. has stopped humanitarian# assistance.

Sorry.

It has stopped funding for## UNRWA temporarily.

But U.S. and quietly Israeli# officials are acknowledging, you see how much## UNRWA does right there, these tent cities, all# of the medical help that Gazans need right now.

The freezing of funding, Geoff, is expected to be# temporary.

And U.S. officials are trying to make## sure that it's as short as possible so that# UNRWA activities are actually not stopped.

GEOFF BENNETT: Nick Schifrin,# thank you for that reporting## and for unpacking all of those# NICK SCHIFRIN: Thanks, Geoff.