Sanctions against Russia could hurt the US dollar as countries like Iran and China seek alternative currencies for trade: Treasury Secretary Janet Yellen

• US sanctions on Russia could threaten the dollar's hegemony, Treasury Secretary Janet Yellen told CNN.
• But, it would be challenging to replicate the dollar's dominance, Yellen added.
• The Chinese yuan is a competitor to the US dollar, amid Beijing's big ambitions for the currency.

US economic sanctions on countries such as Russia could threaten the greenback's global dominance, Treasury Secretary Janet Yellen told CNN Sunday.