The U.S. 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 6-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 U.S. 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.