WASHINGTON (AP) — President Donald Trump is suggesting he has left standing orders for the U.S. military to destroy Iran “ at levels they've never seen before ” if Tehran follows through on its long-standing threats to kill him.

But the U.S. government has no way to create an automatic, preauthorized “dead man’s switch” that would prompt immediate retaliation.

Instead, if Trump were killed, the transfer of power to his successor is governed by the 25th Amendment and the Presidential Succession Act of 1947. Vice President JD Vance instantaneously would become commander in chief and have authority for any retaliation.

Under such a scenario, Vance could do exactly what Trump called for, though there also is a chance he could decide not to follow his predecessor's orders — or offer a direct response in a different way.

“The U.S. has, for a whole variety of reasons, never utilized a technical ‘dead man’s switch,'” said Garrett M. Graff, author of “Raven Rock: The Story of the U.S. Government’s Secret Plan to Save Itself -- While the Rest of Us Die.”

The United States does have extensive contingency plans for continuity of government in the event of a nuclear attack or other major catastrophe that wipes out most or all of Washington. But those plans also do not allow for immediately launching retaliatory strikes upon the death of a president, even if that president had demanded that the military be ready to do so.

Trump nonetheless posted on his social media website Saturday that Iran had made threats “to assassinate, or attempt to assassinate” him and he said 1,000 “missiles are Locked and Loaded and aimed at the Islamic Republic of Iran, with thousands more to immediately follow, should the Iranian Government act on its threat.”

Iran's supreme leader, Mojtaba Khamenei, said hours later that Iranians would continue to avenge the killing of his father, Ayatollah Ali Khamenei. The elder Khamenei died in the initial U.S. and Israeli strikes that stared the war in late February, and he was mourned in funeral events throughout Iran this week. His son said retaliation “is the will of our nation and must certainly be carried out.”

“We pledge to take revenge for the pure blood of you and all the martyrs of these two wars from the criminal and disgraceful killers," he said on remarks aired on state television. "This revenge is the will of our nation and must certainly be carried out.”

The White House on Saturday did not immediately answer questions about what would become of Trump's military orders should he be killed.

During those recent funeral events, mourners repeatedly held posters or banners calling for Trump to be killed along with Israeli Prime Minister Benjamin Netanyahu.

The Wall Street Journal reported this week that Israel alerted U.S. officials to fresh Iranian plots to kill Trump. The White House has refused to comment, but Trump appeared to reference to such threats in comments during this week's NATO summit in Turkey, saying, “They want to take out the U.S. leader — me.”

Sabrina Singh, former Biden administration deputy Pentagon press secretary, said “Iran wanting to target senior American leaders is something that we know is happening."

“You have to take these as credible threats,” Singh said.

US retaliations would almost certainly come, just not automatically

Trump was targeted in two domestic assassination attempts during the 2024 presidential campaign and saw a gunman storm the White House Correspondents' Association dinner he was attending in April.

The president flew part of the way back to Washington from Turkey this week aboard an older Air Force One jet rather a new Qatari-gifted aircraft, raising fresh security questions about the newer plane. Images of the jet, which was retrofitted at an estimated cost of $400 million, show it is not equipped with some of the same missile detection and countermeasure systems as earlier versions.

The swap occurred as the U.S. and Iran once again began trading strikes, jeopardizing last month's initial deal to end the war. Asked about Iranian threats, Trump told reporters aboard Air Force One, “I’m No. 1 on their list."

Graff said the U.S. prepared years of plans for how nuclear launch authority would devolve in the event of a surprise attack. That included, during 30 years of the Cold War, the country keeping fleets of airborne command posts flying 24 hours a day with a general aboard one of them who could take over nuclear launch orders in the event Washington was lost.

“What I believe Trump is saying is that he’s left standing orders to attack if he’s killed, e.g., that the Pentagon should proceed with standard launch protocols,” Graff said. “There’s a lot of reason to doubt the legality of such standing orders, since in the event of a president’s death, the nuclear launch authority would immediately pass to the vice president or designated successor — and ultimately it would be up to him or her to determine whether to proceed.”

Trump’s post only refers to firing missiles at Iran, which the U.S. has done scores of time since its war with Iran began. He did not expressly threaten involving nuclear weapons.

Graff said that, in addition to leaving standing orders in case of his death, Trump also might say “something to Vance like, ‘If I’m killed, nuke Iran,'" and that would make ”more sense and would be absolutely legal”

Biden administration once warned Iran about Trump, too

Washington receiving credible threats against the president and top U.S. leaders from Iran and other foreign adversaries is not uncommon and is often disclosed via national security briefings or other classified means. But far less common is Trump declaring publicly that he personally has been targeted by Iran.

Still, this is not the first time Washington has threatened Iran over threats against Trump.

In 2022, the Biden administration warned Iran against attacking U.S. citizens after the Justice Department's disclosure that a member of Iran’s Islamic Revolutionary Guard Corps had planned to assassinate John Bolton, Trump's first-term national security adviser. Now a Trump critic, Bolton last month pleaded guilty to illegally retaining classified documents in a case led by Trump’s Justice Department.

President Joe Biden’s national security adviser Jake Sullivan said in 2022 that “should Iran attack any of our citizens, to include those who continue to serve the United States or those who formerly served, Iran will face severe consequences.”

Two years later, in the heat of Trump’s campaign against Democrat Kamala Harris, Biden's vice president, the Biden administration again quietly warned Iran. This time, officials made clear that an attack on Trump would be considered an act of war.