Tensions are soaring across the Middle East after Washington vowed to respond to a drone attack by Iran-backed militants that killed three American soldiers.

Conflicts across the region have escalated dramatically since the start of the Israel-Hamas war in October. But does that mean a wider war is likely?

The Sunday strike, which U.S. officials say was launched at a base in Jordan by an Iran-backed group from across the border in Syria, comes as a U.S.-led naval coalition fights Houthi rebels in the Red Sea.

Iran-backed Hezbollah has launched waves of rockets from Lebanon and Israel has hit back. The war in Gaza between Israel and Hamas — which has taken tens of thousands of lives and unleashed a humanitarian catastrophe — continues unchecked.

The entire region is now braced for more violence.

Will the U.S. respond?

In an address following the attack in Jordan, U.S. President Joe Biden laid the blame squarely on “radical Iran-backed militant groups operating in Syria and Iraq,” and pledged retaliation “at a time and place of our choosing.”

Iran denies direct involvement, saying groups in the region "do not take orders from Iran in their decisions or actions."

A direct conflict between Iran and the U.S. has threatened to erupt many times over the past decades, but has been avoided by both sides.

However, Biden’s domestic political rivals point out there have been more than 160 attacks on American troops since the start of Israel’s assault in Gaza, and accuse the White House of not doing enough to deter Tehran.

“He left our troops as sitting ducks," claimed Republican Senator Tom Cotton. "The only answer to these attacks must be devastating military retaliation against Iran's terrorist forces, both in Iran and across the Middle East."

When in power, however, both Republicans and Democrats have shied away from launching an outright confrontation with Iran.

Former President Donald Trump, who is the favorite to secure the Republican Party nomination to challenge Biden, threatened to attack Iran during his presidency but never actually did so — instead hitting Tehran with sanctions and striking its regional proxies.

Trump did, however, order an airstrike in Baghdad in 2020 that killed Qasem Soleimani, the commander of the Quds Force, a division of the Iranian Revolutionary Guards responsible for extraterritorial and clandestine military operations. Tehran threatened a massive response but in the end pulled back from the brink.

Hawks in Washington cite this as evidence that Biden could be much stronger with Iran and not trigger more serious retaliation.

Still, Héloïse Fayet, a researcher at the IFRI think tank in Paris, said the U.S. is unlikely to strike Iran directly unless it can be proven that Tehran ordered the attack.

“The answer from the U.S. will likely be strikes on [Iran's] partners,” she said.

That was also the assessment of Andrew Borene, a former U.S. intelligence official and director of global security at intelligence firm Flashpoint.

"The risk calculus involving war with Iran itself won’t be easy, and must include assessments of any Iranian nuclear capability along with the regime’s next moves," Borene said. "It will also demand assessing the positions of America’s partners and allies in the region such as Saudi Arabia, Jordan, Turkey, Israel and Egypt."

Will Washington be supported by its allies?

Aside from the consistently loyal U.K. — not likely.

Consensus is growing that without a common strategy and with divergent interests in the region, Washington’s European allies won't become actively involved.

“There is no appetite among European countries for a major conflict with Iran in the Middle East,” Fayet said. “Europe should be concerned but it’s difficult to deal with this at the same time as Ukraine, so it’s likely the Europeans will leave the U.S. to resolve these problems by themselves.”

That's not to say European allies aren't stepping up in some way.

Italy, Germany, Belgium and other EU countries have promised to send vessels to patrol the Red Sea, while the foreign ministers of member countries are due to meet February 19 to discuss an EU mission to the region.

France has two naval vessels in area, the Alsace and the Languedoc — which has fired missiles to take down Houthi drones. However, the ships aren't formally participating in the U.S.-led Operation Prosperity Guardian in the Red Sea.

The U.S. and the U.K. carried out multiple inland strikes against the Houthis and have reserved the right to take further action if tankers and container ships using the busy waterway continue to be harassed.

Earlier this month, French President Emmanuel Macron told reporters that Paris hadn't joined those attacks to avoid “escalation.”

What does the crisis mean for energy?

The Red Sea is one of the world’s most important thoroughfares for oil and gas shipments, but so far the impact on energy markets has been limited — even though major shipping firms have ordered their vessels to take the long way around Africa’s Cape of Good Hope instead of via the Suez Canal.

On Saturday, however, a tanker owned by multinational Trafigura was set ablaze after being hit by a Houthi missile while carrying Russian naphtha fuel. While there were no crew injuries and the vessel has since been escorted to a safe harbor, the incident underlined the growing danger to energy markets and could persuade other operators to avoid the area.

A more radical option for Iran would be to close the Strait of Hormuz — which links the Gulf with the Indian Ocean and accounts for about a fifth of global oil traffic.

Martin Kröger, head of the German Shipping Association, said such a move would have profound consequences for European and global energy: “A lot of energy traffic by sea is actually going through that strait, so the impact would be quite severe.”

Why are food supplies being affected?

Recent avoidance of the Red Sea by cargo ships is having a more immediate impact on fruit and vegetables. Unlike oil and gas, perishable agricultural products can’t easily be rerouted around the Cape of Good Hope, which adds up to three weeks in transit time.

That means fresh produce risks rotting en route to Europe, according to Marco Forgione, director general with the Institute of Export & International Trade, who warned that if the conflict continues, it will “tear into the wider food economy” and could affect the Continent’s supply of everything from meat to tea and coffee. 

Particularly hard hit are Mediterranean nations like Italy, Greece and Cyprus, which had previously benefited from quick access to the Suez Canal.

Could the U.S. take a tougher line?

While the scale and target of Biden’s promised response is not yet clear, any unilateral move is likely to draw blowback from key allies in the Middle East who worry about sparking a regional war.

Saudi Arabia has pushed for restraint in dealings with Tehran and fears the economic cost of regional instability.

Turkey, a key NATO ally, has denounced Israel's campaign in Gaza, while President Recep Tayyip Erdoğan has accused the U.K. and the U.S. of trying to turn the Red Sea into a "sea of blood."

“Turkey does not want to be drawn into this conflict because it shares a border with Iran,” said Selin Nasi, a visiting fellow at the European Institute of the London School of Economics. “If the U.S. as its main ally in NATO gets involved in this military conflict directly then Turkey has to choose a side, and that will mean it’s harder to maintain a balanced approach — like it has done with the war in Ukraine.”

The challenge for Biden is how to retaliate without risking escalation by Iran and its partners in the region. Conversely, doing nothing — especially after having said he would avenge the deaths of the three U.S. soldiers — would leave him vulnerable to a charge of weakness from Trump.

“Iran’s leadership probably calculates that the United States will be reticent to fulsomely respond in any manner that would risk escalation of tensions in the Middle East and spark the region-wide [conflict] the Biden administration has admirably tried to prevent the past three months,” said Jonathan Panikoff, a former U.S. deputy national intelligence officer.

But the U.S. may have “to undertake a more fulsome response to restore deterrence,” he added.

Jamie Dettmer, Jeremy Van der Haegen and Laura Kayali contributed reporting.