The Wall Street Journal reports North Korea tried to sell a form of lithium metal to unidentified international buyers last year. 

Citing a UN report, the Journal said Pyongyang attempted to sell the material to undisclosed buyers last year. Lithium-6 is a key material for making miniaturized nuclear weapons. 

A UN panel of experts that track North Korea's weapons programs said a front company run by a state-owned North Korean corporation attempted to sell the lithium online. 

Enriched lithium, or lithium-6, can be used to produce tritium, which increases the explosive power of nuclear detonations, and can be used in bombs with smaller amounts of uranium or plutonium. 

And small nuclear warheads produced this way can be loaded onto intercontinental ballistic missiles.

U.S. lawmakers have requested a briefing by the State Department and intelligence agencies on the UN report and Pyongyang's attempted sale of lithium.

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