The fact-checking website PolitiFact has determined that statement, which Trump first made on the campaign trail, is mostly false.
"We had Hillary Clinton give Russia 20 percent of the uranium in our country. You know what uranium is, right? It's a thing called nuclear weapons and other things. Like lots of things are done with uranium, including some bad things," Trump said during a press conference.
The claim isn't true. Between 2009 and 2013, Russia's atomic energy agency, Rosatom, purchased a majority stake in a Canadian company called Uranium One, The New York Times reported in 2015. The Toronto-based firm's mining assets in Wyoming, Utah and elsewhere in the United States account for about 20 percent of U.S. uranium production capacity, according to the Times.
PolitiFact pointed out that 20 percent of uranium capacity is different from 20 percent of existing uranium. Moreover, the State Department was one of nine government agencies that had to sign off on the deals. Other federal and state regulators also had to approve them.
Clinton was the nation's top diplomat when the sales took place, and the Obama administration was still trying to reset relations with Moscow at the time, PolitiFact noted.
However, Clinton did not represent the State Department on the panel of agency officials who approve deals such as the Uranium One transaction. The representative at the time, former Assistant Secretary Jose Fernandez, told the Times, "Mrs. Clinton never intervened with me on any C.F.I.U.S. matter," referring to the Committee on Foreign Investment in the United States.
The national security question raised by the transaction at the time centered on whether it would make the United States reliant on foreign sources of uranium, not on the proliferation of nuclear weapons, the Times reported. The United States and Russia had exchanged enriched and raw uranium for years, according to the Times.