New York's attorney general is suing the Trump Foundation, as well as Donald Trump and his children, alleging extensive and persistent lawbreaking.
Barbara Underwood said the charitable foundation had engaged in unlawful political coordination designed to influence the 2016 election.
The lawsuit seeks to dissolve the foundation and US$2.8 million in restitution.
The foundation denied the charges, calling them politically motivated.
The president hit back at the lawsuit on Twitter, noting that he would not settle the case.