The U.S. is bolstering its military presence in the Middle East after an American strike killed a key Iranian commander in Iraq, with plans to send about 2,800 troops from the Army’s 82nd Airborne division to Kuwait.

The new U.S. contingent will join roughly 700 troops dispatched to Kuwait earlier this week as part of the division’s rapid-reaction “ready battalion,” according to two U.S. officials who asked not to be identified discussing the deployment. The U.S. already had about 60,000 personnel in the region.

The move comes after Donald Trump ordered a U.S. airstrike that killed one of Iran’s most powerful generals and sent global markets reeling as the president said the military leader was plotting attacks on Americans.

Secretary of State Michael Pompeo said earlier Friday that the strike was in response to the threat of an “imminent attack.” He would not provide details about the threat other than to say it was confined to the Middle East and that U.S. intelligence justified the airstrike.

Iran’s Supreme Leader quickly threatened “severe retaliation” in response. The U.S. State Department has issued a directive urging American citizens to leave Iraq immediately due to the tensions.

After the strike, Pompeo called counterparts and officials in France, the U.K., China, Russia, Saudi Arabia, Afghanistan and Pakistan, reiterating his message of de-escalation, according to the State Department.

Oil futures in London and New York at one point surged by more than 4%, gold hit the highest in four months and 10-year Treasury yields headed for the biggest drop in three weeks. The S&P 500 Index fell less than 1 per cent, paring losses that were poised to be the biggest since October as some stock investors took the opportunity to hunt for bargains.

Soleimani, who led proxy militias that extended Iran’s power across the Middle East, was killed in a strike in Baghdad authorized by Trump, the Defense Department said in a statement late Thursday. Trump, who is staying at Mar-a-Lago resort in Florida, said on Twitter Friday that “Iran never won a war, but never lost a negotiation!” and the U.S. embassy in Baghdad urged its citizens to leave the country.

“We don’t seek war with Iran,” Pompeo said in an interview on Fox Friday morning. “But we, at the same time, are not going to stand by and watch the Iranians escalate and continue to put American lives at risk without responding in a way that disrupts, defends, deters and creates an opportunity to de-escalate the situation.”

“At the direction of the president, the U.S. military has taken decisive defensive action to protect U.S. personnel abroad by killing” Soleimani, the Pentagon said. “General Soleimani was actively developing plans to attack American diplomats and service members in Iraq and throughout the region.”

Pompeo said the decision to strike was based on intelligence collection and that the attack “saved American lives.”

The death of Soleimani, who led the Revolutionary Guards’ Quds force, fueled concerns that the U.S. and Iran could be drawn into an armed confrontation that could easily pull in other countries. The pressures, which have been building for months, have been complicated by widespread protests in Iraq and Iran.

“Qassem Soleimani embodied Iran’s extraterritorial activism in the Middle East,” said Asif Shuja, a senior research fellow at Singapore’s Middle East Institute. “His assassination is thus bound to be a turning point.”

Iran’s top leaders all condemned the attack and vowed to hit back while Foreign Minister Javad Zarif denounced the killing on Twitter as “an act of international terrorism.” Supreme Leader Ayatollah Ali Khamenei took part in an emergency meeting of Iran’s Supreme National Security Council for the first time, the state-owned Hamshahri newspaper reported. He vowed to avenge Soleimani’s killing.

“A severe retaliation awaits murderers who have the blood of Soleimani and that of other martyrs on their wicked hands from last night’s incident,” Khamenei said in a statement.

The Iranian leadership is signaling that it will likely target U.S. military installations and bases in the Middle East and mobilize its network of militias across the region. One official told the state broadcaster that some 36 U.S. military bases and facilities are within reach of Iran’s defense forces, with the closest being in Bahrain. A spokesman for the Revolutionary Guards said the assassination marked the start of a “new phase” in the activities of Iran’s “resistance forces” throughout the region.

A September attack on Saudi oil facilities -- for which Iranian-backed rebels in Yemen claimed responsibility -- highlighted the potential impact of Tehran’s response.

Trump’s European allies urged the president to find a way to ease the tensions with Tehran and warned of the risks that a cycle of retaliations would spiral out of control.

French President Emmanuel Macron is speaking to his counterparts in the Middle East in an effort to prevent the situation spiraling out of control, European Affairs Minister Amelie de Montchalin said on RTL radio. “This is what we feared,” she said. “It’s a continuation of the escalation that’s been happening over recent months.”

German Chancellor Angela Merkel’s spokesman said the U.S. had been provoked by Iran and urged all sides to reduce the tensions.

Soleimani was hit in a U.S. drone strike near Baghdad International Airport, according to a U.S. official. Details remained unclear, but a person familiar with the developments said an Iraqi militia leader, Abu Mahdi al-Muhandis, was also killed.

Iraqi Prime Minister Adil Abdul-Mahdi’s office said the attack was an “aggression against the Iraqi state, government and people” and called for an extraordinary session of parliament.

The Iranian regime will be under “strong pressure” to strike back, said Paul Pillar, a former U.S. Central Intelligence Agency officer and a non-resident senior fellow at Georgetown University in Washington. “Many Iranians will regard this event the same way Americans would regard, say, the assassination of one of the best known and most admired U.S. military leaders.”

Iraqi forces enhanced security around the U.S. embassy in Baghdad after the airstrike, Iraq’s al-Sumaria news reported, citing a security official. Iran summoned the Swiss envoy in Tehran, who helps look after U.S. interests in the country, in response to the killing, according to foreign ministry spokesman Abbas Mousavi.

Soleimani, a veteran of the Iran-Iraq war, was a household name in Iran where he’s celebrated for helping to defeat Islamic State in Iraq and Syria and countering U.S. influence.

He had been sanctioned by the U.S. since 2007 and last May Washington designated the Revolutionary Guards Corps in its entirety a foreign terrorist organization, the first time the label has been applied to an official state institution or a country’s security forces.

The assault in Baghdad marked the latest in a series of violent episodes that have strained already hostile relations between Iran and the U.S. Last week an American contractor was killed in a rocket attack on an Iraqi military base in Kirkuk. That led to a rare, direct American assault on an Iran-backed militia in Iraq and then came the attack on the U.S. embassy in Baghdad.