A decade before he launched the celebrated Fort Lauderdale Trump Tower, Felix Sater hatched a bold plan to keep out of prison.

Charged in a New York securities scandal, the 46-year-old businessman traveled to his native Russia where he took on a unique role that went far beyond flipping on dangerous criminals.

He began spying for the CIA.

Tapping into the vast underground of the former Soviet Union, Sater was able to track down a dozen Stinger missiles equipped with powerful tracking devices on the black market.

With the backing of U.S. agents, Sater agreed to buy the weapons — keeping them out of the hands of terrorists. In return, the CIA pledged to keep Sater from going to jail in the stock scam he concocted with New York organized crime figures.

The deal was set.

Damage ‘incalculable’

Now, years after the failure of the Trump Tower, a legal battle has ensued between burned investors trying to reveal Sater’s background and federal agents who say national security is at stake.

“The problem is at scandal level, and the damage done to victims is incalculable,” argued attorney Richard Lerner in a brief before the U.S. Supreme Court.

Next month, a New York federal judge will decide whether to release dozens of documents in a dispute that alleges Sater stole millions from investors while he was given sweeping protections by prosecutors.

Saying the government has a duty to protect witnesses, prosecutors are fighting to keep Sater’s case hidden in a battle that’s expected to be heard by the justices.

Even the federal judge, Leo Glasser, has weighed into the case, arguing in a hearing that revealing some of the secrets could “significantly affect matters of national interest.”

Though the federal prosecutor’s office in Brooklyn has declined to talk about Sater’s role with the government, records just released show he was finally sentenced in 2009 — 11 years after he was charged in the New York stock fraud case.

The outcome: a $25,000 fine, no prison time.

In addition, he was not ordered to pay back his victims — mandatory under federal law — despite losses totaling $40 million.

What remains sealed is the work that Sater performed for the government in the past 14 years that’s now the topic of the court fight.

During one hearing, the judge said the case had reached top members “of a national law enforcement security agency. I should say agencies — plural.” But he didn’t elaborate.

The fight has been taken so seriously the judge is using the name John Doe instead of Sater to hide his identity and to “protect the life of the person.”

Despite the drama over hiding his past, some details have been divulged over the years, including records in the National Archives that show he cooperated with prosecutors in the securities scheme.

Then, another defendant in the scam, Salvatore Lauria, co-wrote a 274-page book in 2003 describing the deal they cut with the CIA to stay out of prison.

“We were hoping for a free ride or a get-out-of-jail-free card for our crimes on Wall Street,” he wrote in The Scorpion and the Frog: High Crimes and High Times.

When Sater was charged in the securities scandal in 1998, he was already in Russia with another defendant, Gennady Klotsman, according to the book, which used a pseudonym for Sater.