U.S. Sen. Sherrod Brown (D-Ohio) has asked the U.S. Treasury Department to assess whether President Trump and his family’s investment partners and business associates from Russia and other countries have violated anti-terrorist financing, sanctions, or money laundering laws.

Brown is the ranking member of the U.S. Senate Committee on Banking, Housing, and Urban Affairs, which has jurisdiction over a range of issues related to economic sanctions and illicit financing.

In a letter to Treasury Secretary Steven Mnuchin, Brown said the President’s “refusal to divest from investments that pose potential conflicts of interest raises concerns about his and his family’s extensive international holdings and relationships.”

The lack of transparency, Brown said, calls into question whether those interests may pose conflicts with federal laws and rules to combat terrorist financing, money laundering, and other illicit finance risks, either now or in the future. Brown asked Mnuchin if he has requested or received from the President and his family a comprehensive list of their investors, business partners, politically exposed persons and related actors. If not, he was asked to compile such a tally.

“President Trump’s refusal to disclose his business dealings makes it unclear whether he and his family may be exposed to terrorist financing, sanctions, or money laundering risks through their relationships with investors and associates from Russia and other nations,” Brown wrote.

Brown noted that Donald Trump Jr. said in 2008 that Trump’s businesses “see a lot of money pouring in from Russia.” “If so, what is the nature of those ownership or investment arrangements?” he wrote. “Might they provide opportunities for economic leverage over the President or any of his family members or associates?  Do they put the President or his family in danger of violating U.S. statutes, regulations, or simply prudent standards of conduct for the leader of our nation?”

“As Treasury Secretary, you are responsible for policing U.S. firms’ and individuals’ compliance with anti-terrorism, bank secrecy, sanctions and anti-money laundering laws and regulations,” Brown added.

He stressed that concerns are not limited to Russian business ties. According to the President’s public financial disclosure forms, he and his family reportedly have, or have had, significant investments or business ties in over two dozen countries, including Egypt, Azerbaijan, Georgia, Indonesia, Panama, the Philippines, Saudi Arabia, Turkey, Qatar, the UAE, and Uruguay.