(Bloomberg) -- The US and its allies believe major missile or drone strikes by Iran or its proxies against military and government targets in Israel are imminent, in what would mark a significant widening of the six-month-old conflict, according to people familiar with the intelligence.

The potential assault, possibly using high-precision missiles, may happen in the coming days, the people said, requesting anonymity to discuss confidential matters. It is seen as more a matter of when, not if, one of the people said, based on assessments from US and Israeli intelligence. 

Brent crude, the global benchmark, spiked more than 1% to trade above $90 a barrel following the news. Oil is up 16% this year, buoyed by war risk premium since the conflict in the Middle East began.

Iran has threatened to hit Israel in retaliation for an attack on a diplomatic compound in the Syrian capital of Damascus last week that killed senior Iranian military officials. Israel has not explicitly acknowledged it was behind that attack, though it has traditionally followed a policy of ambiguity on operations in Syria, Lebanon and elsewhere.

Israel’s Western allies have been told Israeli government and military facilities may be targeted but civilian facilities are not expected to be, they said. US officials are helping Israel on planning and sharing intelligence assessments, the people said. Israel has told allies it is waiting for this attack to take place before launching another ground offensive against Hamas in Rafah in Gaza, though it’s not clear how soon that operation may begin.

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US and Western intelligence indicates an attack from Iran and its proxies may not necessarily come from Israel’s north, where Tehran’s ally Hezbollah in Lebanon is located, the people said.

Israeli officials are in agreement with the allied view. They’ve also publicly threatened Iran that if it hits Israeli soil, Israel will hit Iranian soil.

Earlier on Wednesday Iran’s Supreme Leader Ayatollah Ali Khamenei repeated a vow to retaliate against Israel for the Damascus strike, which he said was tantamount to an attack on Iranian territory.

Foreign diplomatic missions already are preparing for the potential strikes, making contingency plans for evacuation amid requests from Israeli authorities about emergency supplies like generators and satellite phones, one of the people said, noting that they were not aware of any western missions planning immediate evacuation.

While the US has pushed Israel for a cease-fire in Gaza, the Biden administration has also signaled it’s prepared to back the country in the event of an attack by Iran or its proxies.

“We also want to address the Iranian threat to launch a significant - they’re threatening to launch a significant attack in Israel,” President Joe Biden said Wednesday. “As I told Prime Minister Netanyahu, our commitment to Israel security against these threats from Iran and its proxies is iron clad. Let me say it again, iron clad - all we can to protect Israel’s security.”

It’s not yet clear whether a potential attack by Iran and its proxies would turn the conflict into a broader, more prolonged war or remain contained, one of the people said. A direct Iranian strike on an Israeli city would be a first and intensify hostilities in a major way. Last week, Israel scrambled navigational signals over the Tel Aviv metropolitan area in preparation for a potential attack.

Israeli embassies have also been considered targets for potential attacks in the wake of the strike on Damascus last week, with several missions around the world shuttered.

Iran’s main proxy group is Hezbollah, which is based in southern Lebanon and has been trading fire with Israeli forces almost daily since the war in Gaza erupted in October. Since the start of the war, tens of thousands of people have been evacuated from northern Israel and southern Lebanon.

--With assistance from Golnar Motevalli.

(Updates with oil price rising in third paragraph.)

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