Former President Donald Trump has repeatedly been accused of leaking U.S. secrets, but the latest allegations against him involve key details about some of the most sensitive weapons in the U.S. nuclear arsenal.

Trump gave key details on the U.S. Navy’s elite submarine fleet — including the number of nuclear warheads they can carry and how close they can get to Russian vessels without being detected — to Australian billionaire Anthony Pratt, who passed the information on to dozens of friends and contacts, according to ABC News and The New York Times.

“Sharing top secret details not only threatens that stealth advantage but puts the lives of Sailors at risk and undermines our national security,” Rep. Joe Courtney, a Connecticut Democrat, told Bloomberg News.

The alleged disclosure is only the latest in a string of cases that raise grave questions about Trump’s willingness to keep the nation’s secrets — an issue that’s only going to remain front and center given his commanding lead in the polls to secure the Republican nomination to challenge President Joe Biden again next year.

“Very few people in the U.S. government know the exact configuration of the nuclear subs,” said Joe Cirincione, a security analyst who held the highest clearance level when he worked in Congress on nuclear weapons issues. If true, Trump’s disclosure gets to the heart of U.S. capabilities, he said.

“I never knew the exact payload of our nuclear subs nor the details of our anti-submarine warfare capabilities,” Cirincione said. “I did not have a need to know. The Australian billionaire didn’t have a need to know either.”

Trump is already battling a federal indictment on 40 counts of allegedly holding on to classified documents at his Florida mansion after he left office, disclosing details of war plans to civilians, and obstructing government efforts to get the documents back. Those documents — which included assessments from the Central Intelligence Agency and the National Security Agency — were purportedly left unattended in a bathroom and on a ballroom stage.

And early in his presidency in 2017, reports said Trump revealed sensitive intelligence information from Israel to Russia’s foreign minister and ambassador.

In a social media post, Trump called the submarine allegations “false and ridiculous,” arguing that he was only telling Pratt that the U.S. makes the best military equipment in the world. He called the claim a bid to interfere with the election.

The reports will also only further underscore the deep and growing unease among allies about the U.S.’s ability to keep intelligence out of the public eye, especially if Trump wins re-election. Allied doubts have only been confirmed after a series of hacks allegedly committed by U.S. adversaries such as Russia and China, and leaks from within.

“If there’s an information sharing arrangement in effect and then information is disclosed in an inappropriate way, there’s every reason to think that people are going to be reluctant to share,” said Bradley Martin, who retired from the Navy after 30 years and is now a senior policy researcher at RAND Corporation.

Pratt is one of more than 80 people that Special Counsel Jack Smith’s office identified as potential trial witnesses in the classified documents case in Florida, according to a person familiar with the matter who wasn’t authorized to discuss it publicly. He was interviewed at least twice this year by U.S. law enforcement agencies, according to ABC.

Experts on U.S. submarine technology said Trump’s disclosures, if true, could expose key details about its submarines’ tactical abilities. The U.S. Navy refuses to confirm or deny the presence or number of nuclear weapons on certain vessels. And telling others how close subs can get to adversaries could erode U.S. attack submarines’ tactical advantage as they evade and stalk adversaries.

“The sub silencing data is very hush,” said Hans Kristensen, director of the Federation of American Scientists Nuclear Information Project. “People have gone to jail for revealing that kind of information.”

Rand’s Martin said he doubts whether the secrets will disadvantage the Navy. The number of warheads on a U.S. submarine likely wouldn’t surprise rivals such as Russia, he said, and the U.S. is always working to make submarines quieter in ways that might render Trump’s information out of date.

While the U.S. military will take actions to mitigate the damage, Martin said, “they shouldn’t have to be doing that every 10 minutes.”

(Tony Capaccio and Zoe Tillman contributed to this report.)