The relationship between former President Bill Clinton and a group of wealthy Canadian mining investors who made significant contributions to the Clinton family's foundation has come under scrutiny after their uranium company ended up in the hands of the Russians.

That deal, which gave the Russians access to part of the U.S. uranium reserves, all started with Bill Clinton's dealings with friend Frank Giustra.

Peter Schweizer, author of the forthcoming book, "Clinton Cash," that details family foundation donations and alleged favors, told Fox News that Clinton traveled in 2005 to Kazakhstan, where Giustra, a Canadian investor, was trying to "get control to buy a couple of uranium mines." "And he became, really, partners, in a way, with Bill Clinton-- working on philanthropic activities," he said.

At the same time, Schweizer said, "Giustra has been involved in helping to facilitate speaking engagements -- for the Clintons."

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New York Times reporter Jo Becker, who spent months investigating the deal before publishing a story Thursday, said Guistra and Clinton were both "whisked to the [palace] of President Nazarbayev in Kazakhstan, and it's a fascinating story, because everybody walked away from the table that night with something."

Clinton, Becker said, "basically endorsed" the "progress" Kazakhstan had made on its democracy, though Nazarbayev was elected "with 90 percent-plus of the vote ... in an election that was widely criticized as being rigged."

Schweizer said Clinton even held a press conference with the president and praised his human rights record.

In the end, Giustra got what he wanted.

"The bottom line is after they leave, a couple of days later, Frank Giustra gets his uranium concessions, which end up being enormously lucrative to him and to a small group of Canadian mining investors," Schweizer said.

Becker said his company went from "a worthless shell company overnight -- became this ...huge uranium mining deal."

And then soon after that, Becker said, "Bill Clinton got a huge donation, $31 million from Frank Guistra to his charitable foundation, followed by a pledge to donate $100 million more."

Call by Fox News to the Kazakhstan Embassy were not returned.

Reached for comment, Giustra told Fox News he considers this an old story, and he's not interested in politics.

Meanwhile, his defenders insist that no undue influence was exerted in Kazakhstan because the deal did not require the Kazakh government's approval.

However, Schweizer said, corporate records "indicate very, very clearly that the Kazakh government did have to sign off and approve."

This includes, he said, a memorandum of understanding from 2005 "between the Ministry of Energy of the Republic of Kazakhstan and Kazatomprom, which is the atomic agency in Kazakh government, so there's no way that they can argue the Kazakh government was not a party to these negotiations."

The story doesn't end there.

According to Schweizer, Kazakh officials wanted to take an equity stake in Westinghouse, a U.S. company that works in the civilian nuclear field.

That would require a review by the U.S. government.

So the potential investors came to America to see the man who could make things happen.

Becker said Guistra arranged for Kazatomprom officials to go to Clinton's house in New York.

"When I first contacted both the Clinton Foundation, Mr. Clinton's spokesman, and Mr. Guistra, they denied any such meeting ever took place," Becker said. "And then, when we told them, 'Well, we'd already talked to the head of Kazatomprom,' who not only told us all about the meeting, but actually has a picture of him and Bill at the home in Chappaqua, you know, and that he proudly displayed ... on his office wall, they then acknowledged that, yes, the meeting had taken place."

So what happened to Giustra's company that benefited from that deal in Kazakhstan? After a merger, it became a uranium giant called Uranium One.

And then, the Russians bought it. That's where the American uranium comes into play.

"Uranium One became very active in acquiring uranium assets actually in the United States itself by 2008, 2009, they were a particularly attractive target for the Russian government," Schweizer said.

And the Russians acquired that target -- acquiring what would amount to 50 percent of projected uranium output by 2015.

In other words, Russia now controls what was projected to be up to half of America's uranium.

Calls by Fox News to Uranium One were not immediately returned.

Meanwhile, former Secretary of State and current presidential candidate Hillary Clinton factors into that deal.

According to Schweizer, in order for that deal to go through, it needs federal U.S. government approval.

"And one of those people that has to approve that deal is Secretary of State Hillary Clinton," Schweizer said.

On Thursday, the Clinton camp pushed back. Campaign spokesman Brian Fallon issued this statement:

"No one has produced a shred of evidence that Hillary Clinton ever took action as Secretary of State in order to support the interests of donors to the Clinton Foundation. To suggest the State Department, under then-Secretary Clinton, exerted undue influence in the U.S. government's review of the sale of Uranium One is utterly baseless. It mischaracterizes the nature of the State Department's participation in such reviews, and also ignores the range of other regulatory agencies that ultimately supported this sale. It is impossible to view this allegation as anything other than just another in the many partisan conspiracy theories advanced in the Clinton Cashbook."

Schweizer told Fox News that when Clinton was the senator from New York, she objected to a foreign government owning U.S. ports and pointed to the serious implications of the Russians getting uranium.

"We're talking about things that related to the nuclear industry. We're talking about the Russian government," he said, noting Russia already provides equipment to Iran.

Further, he said the Clinton Foundation was receiving "tens of millions of dollars from shareholders in Uranium One who wanted the Russian government to acquire them because it would be a financial landfall."

In the end, a Russian company, essentially controlled by Vladimir Putin, will now be in charge of a substantial portion of American uranium.

Given that Russia sends uranium to its client state, Iran, American uranium could well be sent to the very nation the Obama administration is now negotiating with to try to slow its ability to develop a nuclear weapon.