WATCH: FBI informant says U.S. had evidence to block billions in nuclear deals for Russia

In a series of rapid-fire decisions, a young Obama administration cleared the way for Russia to buy a mining company with large U.S. uranium assets, to be freed from Cold War-era nuclear export restrictions and to secure billions of dollars in new American nuclear fuel contracts.

Now nearly a decade later, a longtime FBI undercover informant says the U.S. government had ample reason between 2009 and 2011 to block those decisions: It knew the top American executive of the Russian state-owned nuclear company benefitting from them was engaged in extensive criminal conduct on U.S. soil.

“I was shocked and appalled because I believed that my reporting to the United States government certainly would head off or would, at least, have some type of consideration before approval was made for those acquisitions,” William Douglas Campbell told The Hill in his first on-camera interview.

Campbell has faced questions about the credibility of his account of events due to his memory loss after a brain tumor and because he is accused of engaging in unauthorized payments with Russians while undercover. Campbell disputes those accusations.

A spokesman for former President Obama did not immediately respond Friday to a request for comment.

Campbell spent from 2008 to 2014 undercover as an informant inside Rosatom, the state-owned company at the center of Russia’s uranium empire. During that time, he says he helped the FBI prove Russian nuclear industry figures were engaged in bribery, money laundering, kickbacks and extortion and were carrying out a plan to hurt the United States by making it more dependent on Russian uranium. He even recorded them accepting suitcases full of bribery cash.

“It was all covert work. The Russians had no idea that I was working, that I was interacting with the federal government, specifically the [Department of Justice] and FBI,” he said. 

His counterintelligence work eventually helped the FBI land several Russian and American executives in prison. But those criminal charges were filed years after the first evidence was uncovered, he said, and his FBI handlers described their own frustration at watching Russia win favorable decisions while engaged in wrongdoing.

“Because it was a matter of national security, I felt sure that it was being handled on a high level and I was actually assured of that by agents that this strategy would be offset because it was a liability to our country,” he said.

When he pressed agents why the Obama administration approved the Uranium One mining company purchase and cleared the way for billions in new U.S. nuclear fuel contracts during a “reset” in U.S.-Moscow relations, they gave a simple answer.

“Ask your politicians,” he recalled.

He said he also provided the FBI with evidence Moscow was aiding Iran’s illicit nuclear program and at some point Russian President Vladimir Putin’s top nuclear aides boasted to him how weak they thought the United States was to cede so many favorable decisions to Russia.

“It was very illuminating because of the indications that they made about the influence from the United States government, their arrogance about the weakness of our government. It was not easy to sit there and listen to it,” he told The Hill. “They talked about the weakness of the president ... and in describing the president’s weakness they used racial epithets, which was not good.”

Updated at 5:04 p.m.