According to CoinMeta, U.S. Treasury Secretary Janet Yellen announced new sanctions against Iran, which pushed the U.S. dollar index DXY to a high for the week on Tuesday. Yellen warned that countries and companies doing business with Iran would face U.S. retaliation, but did not specify the measures. Analysts said that the U.S. threat to exclude these countries from the dollar-based financial system has sparked market speculation, and some countries and banks may buy dollars in advance, thereby driving up the dollar.