AMNA NAWAZ: Yemen's Houthi rebels seized more islands in the strategically crucial Bab al-Mandab Strait today and now control the west coast of the country on the Red Sea.

In the meantime, a crucial pipeline in Saudi Arabia will be out of commission for weeks after it was attacked last week, sending oil prices even higher.

Here's Ali Rogin.

ALI ROGIN: Today, more Houthis attacks against Saudi Arabia.

Yemeni fighters say they hit Saudi Arabia's Khamis Mushait air base.

And Saudi Arabia says a Houthi projectile wounded two people and damaged a mosque in the Saudi port city of Jazan, just the latest in the past week, with hundreds hurt on both sides of the border and as the conflict reignites.

Riyadh has turned to the U.S.

for help, but, so far, President Trump has not answered a call for American airstrikes.

And over the weekend, he said the U.S.

has been talking to the Houthis directly.

DONALD TRUMP, President of the United States: We have had discussions.

The Houthis called us, and they don't want to fight with us.

They let us know they don't want to fight with us.

They don't want me to go after -- they don't want us to go after them.

And they're letting most ships go through.

This is one country that they're not too happy with, and we will get that straightened out.

ALI ROGIN: Inside Yemen, Houthis seized more islands near the crucial Bab al-Mandab Strait, the choke point through which roughly a 10th of global trade sails.

And so far it has been an advance met with little pushback, capturing more territory without real resistance from Saudi-backed Yemeni forces.

The Houthis have been expanding their control over Western Yemen along the Red Sea.

They're freeing prisoners once held by Saudi-backed forces and celebrating in Sanaa, the Houthi capital.

Today, they expanded their reach again, capturing the islands of Greater and Lesser Hanish, 100 miles north of the strait, giving them even more leverage over Saudi shipping routes out of the Red Sea.

It follows last week's seizure of the port of Mokha and the island of Mayun inside the strait itself that sparked global alarm over who controls it.

And it matters even more now with Iran and the U.S.

still battling over the Strait of Hormuz.

Saudi-backed Yemeni forces are trying to regroup and fight back.

SULTAN AL-ARADAH, Yemeni Leadership Council (through translator): What happened is a deeply painful event for us, and it stems from reasons that will be thoroughly discussed.

Even the forces that withdrew from one location to another are currently regrouping, God willing, and will return to the battle in one way or another.

ALI ROGIN: A crucial Saudi oil pipeline went down after it was struck last week in an attack Riyadh blamed on Iran-backed militias in Iraq.

It will take weeks to fix.

The kingdom had leaned on that pipeline, 745 miles coast to coast, to move crude away from the blockaded Persian Gulf and out through the Red Sea.

Now that route too is under threat.

The Houthis and Saudis fought a nearly decade-long war that for the last four years had settled into an uneasy cease-fire.

Tensions spiked again in July, when Saudi Arabia bombed a Houthi-controlled airport to stop a plane Saudi officials said was carrying Iranian weapons.

And yet the war resurging threatens yet another humanitarian crisis in one of the most impoverished countries in the world.

Already more than 85,000 people have been displaced inside Yemen since July.

More than 2,000 have already crossed the strait by boat to Djibouti, families with their children displaced again and again in this war arriving with nothing.

For the "PBS News Hour," I'm Ali Rogin.

To help us better understand the state of play in this volatile region and how it might affect the wider war, I'm joined now by Michael Ratney, who served as U.S.

ambassador to Saudi Arabia during the Biden administration.

He's now a senior adviser at the Center for Strategic and International Studies.

Ambassador Ratney, welcome back to the "News Hour."

Thanks for joining us.

MICHAEL RATNEY, Center for Strategic and International Studies: Thank you.

ALI ROGIN: As the Saudis deal with these new attacks, what is it exactly that they're asking for from the United States?

MICHAEL RATNEY: So the Saudis are now under direct attack from their mortal enemies, from the Iranians directly, from Iranian proxies, obviously the Houthis, you were discussing, in Yemen, and from Iranian-backed militias in Iraq.

And they're looking for help from the United States, substantial military support, to help try to push back, disincentivize, at a minimum, the Houthis from continuing these attacks and if possible to vanquish them completely.

ALI ROGIN: The Saudis, though, were engaged in a long war with the Houthis for about a decade, bombed them heavily using American munitions, killing many, many Houthis, and yet that still hasn't seemed to really put them on the back foot.

What would the United States getting involved at this point really gain the Saudis?

What makes them think it would make any difference?

MICHAEL RATNEY: So it's true.

There was a really unfortunate, long and unfortunate experience with the Saudis pursuing military conflict against the Houthis.

It eventually resulted in a suspension of that and pursuit of diplomacy, including this road map with the Houthis that effectively legitimized them as a governing authority.

And that worked.

That held until after the Gaza war started and the Houthis started attacking U.S.

shipping.

There was another U.S.

effort to support military strikes against the Houthis that President Trump suspended.

I think now the calculation is that the Houthis have attacked Saudi Arabia, their energy infrastructure, their -- an oil refinery in the south of the country that has an impact not just on the Saudi economy, but global oil markets at this point.

And I think what the Saudis want is some kinetic support from the United States to push back on that.

It's an unfortunate situation.

In the past, it's true that military strikes haven't worked.

And, frankly, I think, eventually, this is headed for diplomacy again.

But, in the meantime, it's hard for the Saudis not to try to retaliate.

ALI ROGIN: So far, President Trump seems to suggest that such support is not forthcoming.

He said: "The Houthis called us.

They don't want to fight with us," as we mentioned in the piece.

He also said he spoke with Saudi Crown Prince Mohammed bin Salman, who says -- and the president says that everything is going fine and will work out dandy.

How do the Saudis feel about how the United States is treating this conflict?

MICHAEL RATNEY: So, at a minimum, they're extraordinarily frustrated.

When you think about it, the Saudis have pursued a military partnership with the United States for decades, and we with them.

And the whole point of a partnership like that is, at a time of crisis, when you're being attacked, you want support from your partner, from your ally.

The Saudis went so far as to pursue a mutual defense treaty with the United States and the possibility of normalization with Israel.

That's how important it was that they have clarity about their relationship with the United States.

I think that's what they're asking for from -- what they're asking President Trump for at this point is military support, and, if not military support, some manner of support that will help them retaliate, push back, disincentivize the Houthis from continuing these strikes.

It seems like President Trump, as you say, is not that interested in doing it.

He probably sees it as kind of broadening a war that he's hoping has wound down already.

But, at this point, it clearly hasn't wound down, and it probably irritates the Saudis to no end to hear President Trump in Ireland talking about this whole war as a small problem that's something we will be very happy with.

ALI ROGIN: Well, and to that point about trying to wind down this wider war, to what extent do you think the U.S.

is staying out of it because they're already overextended in Iran?

MICHAEL RATNEY: You know, that's part of it.

I think it's true President Trump seems to have a lot of calculations for the Iran war.

He seems to want to get out of it.

He seemed to want to get out of it almost since it first started.

Clearly, one of the problems is that the supply of our most sophisticated munitions is being diminished.

Our Navy is being stretched in.

These deployments are long.

It's having an effect on the U.S.

military's posture at a time when there's other conflicts in the world.

So I think he's probably hearing from military leadership that they can't afford another front.

And for him too, politically, I think he's at a point where he doesn't want to have to keep answering questions about why this war keeps going on and on.

ALI ROGIN: In about 30 seconds we have left, how severely do you think this is going to impact oil markets, given the disruptions already that are taking place in the Strait of Hormuz?

MICHAEL RATNEY: I have the impression that, until very recently, global oil markets were not pricing in the risk that was out there.

I think in some ways, they were hopeful, looking for the next cease-fire, looking for the next kind of piece of evidence that this war was over.

I think now you're seeing the real risk being priced in, closure not just of Hormuz, but potentially the Bab al-Mandab, these Red Sea routes, bombing of Saudi East-West Pipeline.

Now you're seeing oil up near $110, and I think that is a result of all of the risk that's finally being recognized.

ALI ROGIN: Former Ambassador Michael Ratney, thank you so much for your insights.

MICHAEL RATNEY: Any time.