According to Odaily Planet Daily, US Senators Elizabeth Warren and Roger Marshall expressed their concerns about the stablecoin Tether in a letter to US Secretary of Defense Lloyd Austin and Treasury Secretary Janet Yellen. They expressed great concern about countries such as Russia, Iran and North Korea relying on cryptocurrencies to evade sanctions, and believed that the national security threat posed by cryptocurrencies requires a corresponding response from the US defense community. Tether responded that it cooperated with law enforcement agencies to track assets and catch criminals.