AMNA NAWAZ: Another major news story today, this one oversees.

Today, a senior administration official told "PBS News Hour" the U.S.

will reduce the number of U.S.

troops who've been fighting ISIS in Syria.

The statement comes after a major shift in U.S.

policy in the country, removing support from Kurdish forces, who fight ISIS alongside American troops, to support Syria's new president, Ahmed al-Sharaa.

Meanwhile, next door in Iran, the country appears to be bracing for a U.S.

strike.

Nick Schifrin is following all of this, and he joins us now.

So, Nick, let's start with Syria.

What's the U.S.

saying about Syria?

NICK SCHIFRIN: Amna, official, that senior administration official telling me tonight that -- quote -- "The U.S.

presence at scale is no longer required in Syria, given the Syrian government's willingness to take primary responsibility for combating the terrorist threat within its borders."

But a military official tells me this is not a withdrawal of the 1,000 or so troops that have been stationed in Syria.

Instead, it's what this official calls a consolidation.

The U.S.

has already announced it would close two bases in Syria, and the official tells me the final number and location of U.S.

troops is dependent on how capable the Syrian government is to fight ISIS.

For the last decade, though, those U.S.

troops fought ISIS alongside the mostly Kurdish Syrian defense forces, who controlled most of the northeast, and together they liberated the area from ISIS.

But, as you said, the U.S.

is now all in with Ahmed al-Sharaa.

And, recently, central government forces overran Kurdish positions, and the U.S.

withdrew support for the Kurds.

And this past weekend at the Munich Security Conference, I cut up with Mazloum Abdi.

He is the commander in chief of the Syrian Democratic Forces.

And he warns that any U.S.

withdrawal would threaten the political agreement that he made with the central government and the fight against ISIS.

GEN.

MAZLOUM ABDI, Commander, Syrian Democratic Forces (through translator): I believe withdrawing American troops at this critical moment is not a good idea, as it will inevitably present inherent challenges, especially in the ongoing fight against terrorism.

There will be severe negative consequences.

I believe that the presence of the United States is very crucial for implementing existing agreements, achieving stability in Syria, and for the commitment of all parties to the agreements to continue, at the same time for us to continue the fight against ISIS.

NICK SCHIFRIN: But, tonight, a U.S.

military official insists no decision made to go to zero, Amna, and the U.S.

will continue to partner with the Syrian government against ISIS.

AMNA NAWAZ: Another major story you have been tracking now, the U.S.

and Iranian officials met yesterday to continue negotiations over that country's nuclear program.

What have we learned about how that negotiation went?

NICK SCHIFRIN: An Iranian official and a regional official both confirmed to me tonight that Iran has made this offer, a pause in domestic enrichment of uranium to produce nuclear fuel through the end of the first Trump administration, entering into some kind of regional consortium for enrichment in the future, and, three, exporting or diluting the highly enriched uranium -- that's one step away from weapons-grade -- that the U.S.

bombed last summer.

In exchange, Iran would ask for sanctions relief and open up to U.S.

investment.

Officials tell me the U.S.

has made a counteroffer and continues to insist that Iran permanently give up any ability to enrich uranium domestically.

And, today, we heard from White House spokesperson Karoline Leavitt hinting at that ongoing impasse.

KAROLINE LEAVITT, White House Press Secretary: There was a little bit of progress made, but we're still very far apart on some issues.

I believe the Iranians are expected to come back to us with some more detail in the next couple of weeks, and so the president will continue to watch how this plays out.

NICK SCHIFRIN: Leavitt today insisted the president's priority is a deal, but, Amna, the U.S.

has deployed what the president calls an armada to the region, including the U.S.'

largest aircraft carrier and strike group, dozens of additional fighter jets.

Former officials, analysts telling me the U.S.

is capable of delivering a strong blow against Iran, but will find it difficult to defend itself and allies from a big Iranian response.

AMNA NAWAZ: What do those former officials and analysts tell you about the chance of a deal?

NICK SCHIFRIN: Exactly what Secretary of State Marco Rubio has said in the last couple of days.

It is very difficult, because the U.S.

demands are larger than what Iran is willing to concede.

Iran will simply not give up that right for domestic enrichment, says former State Department official and current distinguished diplomatic fellow at the Middle East Institute Alan Eyre.

ALAN EYRE, Middle East Institute: What they see is, any capitulation in the face of pressure will invite further aggression.

What they're doing now is, they're getting ready to take a hit.

Satellite imagery is showing this.

Open press reporting is showing this.

I'm sure intelligence is reporting this.

While they're continuing negotiations with the U.S., they fully expect these negotiations not to result in a deal, and they're preparing themselves for a massive U.S.

military attack.

NICK SCHIFRIN: And those preparations, Amna, include steps like deploying troops across the country, dispersing decision-making authority, and fortifying nuclear sites, all signs, again, that analysts believe Iran is preparing for a U.S.

strike.

AMNA NAWAZ: Nick Schifrin tracking two major stories overseas.

Nick, thank you.

NICK SCHIFRIN: Thank you.