Israel has shared intelligence with the United States asserting that Iran is considering the use of chemical weapons against its adversaries, information met with alarm by some American officials and deep skepticism by others, according to U.S. and regional officials.
Some American officials see the Israeli intelligence as part of a pressure campaign by Prime Minister Benjamin Netanyahu’s government to persuade the Trump administration to return to major combat operations against Iran.
Other officials believe the threats should be taken seriously, given the recent array of warnings about Iran’s preparations to attack American interests.
Israel has shared some of the information with officials in Gulf countries. Several doubted that Iran was developing plans to use chemical weapons and believe Israel is trying to push the United States and its partners to return to a more intense phase of the war.
American claims about Iran’s chemical weapons, or its intent to build them, go back decades. In 2003, Iran acknowledged it had developed chemical capabilities during the Iran-Iraq war in the 1980s but said it later dismantled them.
In recent years, the United States has publicly asserted in its annual unclassified intelligence assessments that Iran “likely aims” to continue its research and development of chemical weapons.
Iran has publicly denied having chemical weapons and previously described such allegations as psychological war waged by Israel and Mr. Netanyahu.
All of the people interviewed for this article spoke on the condition of anonymity, given the secret nature of the Israeli intelligence, the sensitivity of Iranian planning and the classified American discussions.
After eight months of war, the United States and Iran are in something of a holding pattern, exploring the possibility of a diplomatic breakthrough and preparing for renewed warfare.
The debate over the new intelligence shows how tense the moment is and the potential for grave miscalculation. U.S. officials have said the Trump administration has no intention of using a nuclear weapon, but Iranian officials are not so sure.
Mr. Netanyahu is fighting for his political survival after he failed to secure a clear path to forming a government in elections last week. Some analysts believe that the veteran leader may be seeking to use a security emergency as leverage to compel opposition leaders to join him in a coalition.
In recent conversations with U.S. spy agencies and other officials over the past two weeks, Israeli officials have portrayed the chemical weapon threat as more urgent than Iran’s ambitions to develop a nuclear weapon.
The Home Front Command, the Israeli military unit responsible for emergency response and issuing guidance to civilians, is running drills across Israel this week but is not including chemical weapons preparation as a major part of the exercises.
The command has also not issued widespread reminders to its officers or the public regarding safety guidelines for such a possibility, according to two unit officials who spoke on the condition of anonymity because they were not authorized to speak to the news media. The Israeli military declined to comment.
In recent weeks, the U.S. military has built up a vast arsenal in the region, with naval ships, fighter planes and bombers ready to launch a relatively short campaign of intense strikes after the midterm elections, should President Trump authorize action.
At the same time U.S. and other diplomats are trying to forge an agreement with Iran which would reopen the Strait of Hormuz, address Tehran’s nuclear program and put off further military action. The buildup of forces could be intended as much to support that diplomatic push as it is to prepare for a return to war.
Iran has intensified attacks on commercial ships in the Strait of Hormuz, hoping to exert maximum economic pressure on the United States ahead of its elections on Tuesday.
The use of chemical weapons is a particularly fraught issue for Iran, one of a few countries that have suffered the effects of them. During the Iran-Iraq war, Saddam Hussein deployed chemical weapons, killing thousands and leading to decades of health problems among some 100,000 Iranian veterans and civilians, according to Iranian experts.
U.S. intelligence agencies have long tracked Iran’s development of chemical weapons, which are banned under international law. Israeli intelligence agencies have told U.S. counterparts that they believe Iran is moving rapidly to develop the technology to put such weapons on a missile or to sneak them into Israel or another country to use in an attack, according to American officials.
For some American officials, the talk of chemical weapons threats from Iran has evoked the flawed U.S. intelligence in 2002 about Iraq’s weapons of mass destruction. Iraq had largely abandoned or frozen its nuclear, chemical and biological programs by then, but U.S. intelligence agencies told President George W. Bush’s White House that their assessment that Iraq had such weapons was ironclad.
People briefed on the new intelligence had different views on how quickly — or effectively — Iran could deploy a chemical weapon. While mounting a chemical weapon on a ballistic missile is not difficult, ensuring that the weapon can effectively disperse a chemical agent is, according to weapons experts and U.S. officials. Smuggling a bomb across a border also poses challenges.
Using a drone to deliver a chemical weapon is also a possibility.
A regional official said Israel had presented Gulf countries with claims that Iran was working to make its chemical weapons operational. Israeli officials did not share evidence but briefed the officials on their assessments, which the official said Gulf governments found unserious.
The White House did not comment, but a U.S. official said Mr. Trump would keep America and its allies safe from any potential threat. The C.I.A. declined to comment.
A spokesman for Mr. Netanyahu’s office said that “Israel closely tracks every threat posed by the Iranian terror regime and is prepared to deal with it.” A spokesman for Iran’s mission to the United Nations did not return a request for comment.
While there is little debate in the U.S. intelligence community that Iran is developing chemical weapons, there is significant debate over whether its leaders would ever use those weapons, especially if not provoked by further attacks.
The U.S. director of national intelligence warned in 2024 that “Iran probably aims to continue research and development of chemical and biological agents for offensive purposes.”
Dana Stroul, the Pentagon’s top Middle East policy official in the Biden administration, said it had been known for more than two decades that Iran stockpiled components for chemical weapons but that Tehran has never deployed them.
But Iran might feel “existentially pressured and potentially crossed the line to direct offensive use of these unconventional weapons,” said Ms. Stroul, who is now with the Washington Institute for Near East Policy.
The United States has monitored a variety of threats from Iran, as intelligence collection intensified after the discovery of an Iranian plot to attack a military base in Britain used by American warplanes.
On Oct. 23, Jay Clayton, the director of national intelligence, sent Marco Rubio, the secretary of state and national security adviser, a memo warning of the threat of Iranian attacks. U.S. diplomats and other personnel were then put on high alert.
U.S. agencies assess that the threat against Americans in the Middle East and several other countries is at its highest level since the war started in February, U.S. officials said.
U.S. Central Command has a plan to strike Iran beginning as early as Wednesday, after the U.S. midterm elections and when three aircraft carriers are in the region, according to U.S. officials.
The ideal conditions for the type of campaign the military has laid out will last only a short time. After early November, one of the aircraft carriers will need to return to its home port. Early November is also a period of moonless nights, the kind of deep darkness the U.S. military likes to use for its attacks.
Some Trump cabinet members have argued for more time to let a campaign of economic pressure work. They say a U.S. blockade and sanctions on the country will eventually bring down the Iranian government.
But some officials point out that Iran has been able to weather the pressure campaign and that there is little indication that the Iranian government will collapse without additional military attacks.
Stephanie Walker, a senior national security and intelligence official at the F.B.I., said last week that the Iranian threat to U.S. interests was “a top focus right now for the entirety of the U.S. government.”
Tehran’s goals, Ms. Walker said, included espionage, influence and cyberattacks. Iran-linked hackers targeted scores of water systems across the United States this summer, leading some counties to issue boil-water advisories.
Iran has also attempted to impersonate people online in order to dupe their associates into sharing access to sensitive information with them. Artificial intelligence has made this form of trickery far easier, “especially with vishing,” she said, referring to voice-based phishing attacks.
The war “changed Iran’s calculus for what they were willing to do here against us,” Ms. Walker said last week at a national security conference in Sea Island, Ga.
Reporting was contributed by Vivian Nereim and Tyler Pager in Palm Beach, Fla., Maggie Haberman in Washington and Ronen Bergman in Tel Aviv.
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