A confidential FBI warning circulated to law enforcement agencies in California has raised concerns that Iran had aspired to retaliate for US military action by launching drones from a vessel off the American coast, with unspecified targets in the state, as officials stressed there was no evidence of an imminent or credible threat to the public.
The alert, reviewed by ABC News and Reuters, said Iran had allegedly sought to conduct a “surprise attack” using unmanned aerial vehicles from an unidentified vessel “off the coast of the United States Homeland”, specifically against unspecified targets in California, if the United States carried out strikes on Iran. The bulletin added that investigators had no further information on timing, method, targets or perpetrators. Reuters reported that the confidential FBI bulletin was distributed through the Los Angeles Joint Regional Intelligence Center.
The warning emerged as the conflict between the United States, Israel and Iran continued to widen after major US-Israeli strikes began on 28 February. British parliamentary researchers said those strikes were launched by the US and Israel against Iran’s nuclear and ballistic missile infrastructure and were followed by Iranian counter-strikes against Israel, US bases in the region and military and civilian locations in Arab states hosting American forces. The same briefing said the fighting had already triggered significant international concern over escalation across the Middle East.
President Donald Trump publicly framed the opening US action as a mission to destroy Iran’s missile capabilities and end what his administration described as an imminent nuclear threat. A White House statement published on 1 March said Operation Epic Fury had been authorised to “eliminate the imminent nuclear threat” posed by Iran, destroy its ballistic missile arsenal and weaken its proxy networks. In a separate account of Trump’s announcement, the president was quoted as saying: “We are going to destroy their missiles and raze their missile industry to the ground.”
The California alert appears to sit within a broader pattern of US homeland security concern since the war began. ABC News reported earlier this month that a Department of Homeland Security bulletin warned that although a large-scale physical attack was unlikely, “Iran and its proxies probably pose a persistent threat of targeted attacks in the Homeland” and would likely intensify retaliation if the death of Iran’s supreme leader was confirmed. Reuters also reported on 2 March that a US intelligence assessment warned of Iranian attacks on American interests following the reported killing of Ayatollah Ali Khamenei.
Even so, federal, state and local officials have been careful not to suggest that California residents face an immediate danger. Reuters reported that California Governor Gavin Newsom and Los Angeles Mayor Karen Bass confirmed heightened vigilance while saying there were no imminent or credible threats. Reporting from San Francisco also said Mayor Daniel Lurie had been told there was no imminent threat, while state and local authorities remained in contact with federal partners and continued to monitor the situation.
That distinction has become central to how the story is being handled. The FBI bulletin did not say an attack was under way, nor did it identify a launch point, a target list or specific operatives. Instead, it described an alleged aspiration and warned law enforcement agencies to remain alert. That language matters in intelligence reporting, where agencies often distribute raw or partly corroborated information so that police and security officials can prepare without treating every fragment as a confirmed operational plot. Reuters noted that the bulletin offered no specific details beyond the reported scenario of drones launched from sea toward California.
The use of drones is not an incidental detail. US officials have been increasingly concerned about the low cost, accessibility and deniability of unmanned systems, especially if they are launched from outside traditional military theatres. ABC News reported that American intelligence and law enforcement agencies are also monitoring the growing use of drones by Mexican cartels and the possibility that such technology could be adapted for attacks on US personnel or law enforcement. One bulletin reviewed by ABC said an “uncorroborated report” had suggested unidentified cartel leaders had authorised explosive drone attacks against US law enforcement and military personnel along the southern border.
That wider context helps explain why California, and especially its ports and coastline, would be treated seriously in any warning tied to maritime drone launches. California is home to major naval, commercial and population centres, including Los Angeles, Long Beach, San Diego, Oakland and San Francisco. Bloomberg reported that officials at the Port of Los Angeles and San Francisco City Hall had been briefed and were maintaining vigilance despite saying there were no immediate threats. Even absent a confirmed attack plan, the idea of small drones launched from a civilian or disguised vessel presents a challenge for security agencies because it blurs the line between conventional military retaliation and covert asymmetric action.
The political backdrop is equally significant. Trump has repeatedly insisted that US action against Iran was necessary to stop Tehran obtaining a nuclear weapon, while Britain has sought to distance itself from direct participation in the initial strikes. Prime Minister Keir Starmer said on 28 February that “British planes are in the sky today as part of coordinated regional defensive operations to protect our people, our interests, and our allies”, but his government also emphasised that British involvement was defensive. Foreign Secretary Yvette Cooper said it was “simply not true” that the UK was being dragged into another Iraq-style conflict, according to comments reported after an Iranian drone strike on an RAF base in Cyprus.
For now, the California warning remains a story about precaution rather than proof of an impending strike. What is known is that the FBI sent a confidential bulletin to law enforcement, that the bulletin described an alleged Iranian ambition to attack California with drones launched from a vessel offshore, and that senior officials have responded by heightening vigilance while telling the public there is no credible or imminent threat. What is not known is whether any vessel was ever positioned to carry out such an operation, whether any launch capability existed, or whether the intelligence reflected a real plot, a contingency concept or fragmentary threat reporting gathered before the war began.
As the conflict overseas deepens, that uncertainty may be the most important part of the story. The FBI warning shows how seriously US authorities are taking the prospect of retaliation reaching American soil, particularly through unconventional means such as drones. But the official response so far has been calibrated: take the threat seriously, increase coordination, protect critical infrastructure, and avoid overstating what the intelligence actually shows. In a conflict already marked by rapid escalation, secrecy and competing claims, California has become the latest place where distant war is being measured not just by events abroad, but by what security agencies fear could happen at home.