U.S. Treasury Secretary Steven Mnuchin waits to testify before the Senate Banking Committee at hearing on Domestic and International Policy Update on Capitol Hill in Washington, DC, U.S. May 18, 2017. REUTERS/Yuri Gripas

WASHINGTON (Reuters) - U.S. Treasury Secretary Steven Mnuchin on Thursday pledged to treat “very seriously” any business dealings President Donald Trump or his family might have with foreign companies flagged by officials as national security risks.

Mnuchin did not say any such cases existed. A senior Democrat pressed Mnuchin, in an appearance before senators, to produce a list of the Trump family’s business relationships with foreign companies.

Senator Sherrod Brown, the top Democrat on the Senate Banking Committee, said Mnuchin had not adequately responded to his March 2 letter asking if the Treasury had a list of Trump’s business partners to see if any of them were on sanctions lists or had been investigated by a national security watchdog that analyzes foreign investments.

The Treasury released a copy of a March 31 letter responding to Brown which said the department works with other agencies “to address and mitigate potential conflicts of interest if and when they arise.” Mnuchin said he reviewed cases at the Committee on Foreign Investment in the United States (CFIUS) every week. The Treasury is the lead department among the government agencies that are part of CFIUS.

“I can assure you that if there were any cases that involve the president or any members of his family that they would be treated very seriously. We would review them as we would anything else,” Mnuchin told the Senate panel.

Trump, a wealthy real estate developer, has declined to sell his global businesses despite demands from critics that he do so to avoid conflicts of interest. Trump has said his two oldest sons will have daily control of his businesses while he is president.

A Reuters review in March found that at least 63 individuals with Russian passports or addresses have bought at least $98.4 million worth of property in seven Trump-branded luxury towers in southern Florida.