"If Vietnam chooses to ask for assistance in developing an auction, we would be happy to provide assistance to do so," she said in Hanoi when asked about possible auctions to be arranged by Vietnam for new concessions at unexploited mines.

Vietnam's government intends to launch tenders for multiple blocks of its Dong Pao mine before the year's end, Tessa Kutscher, an executive at Australia's Blackstone Minerals Ltd, which plans to bid for at least one concession, told Reuters last month.

Blanchard said that U.S. technical assistance to partner countries can extend to support to craft tenders or bids "to generate the most interest".

(Reporting by Francesco Guarascio; Editing by Martin Petty)