In a suit before a court in Washington, Joseph Kabila who led Congo from 2001 to 2019 wants his name removed from a US Treasury blacklist.
He contends that his sanctioning by the Office of Foreign Assets Control (OFAC) in April was based on unsubstantiated allegations.
Washington accuses Kabila of financing and offering political support to Rwanda-backed M23 rebels who seized two Congolese provinces last year.
But Kabila counters that no transfer of funds or political incentive to the rebels from him is specified by the US government.
After years in self-imposed exile, Kabila emerged in Goma last year only months after the city fell to the rebels.
A Congolese military court has sentenced Kabila to death in absentia for treason and other charges over his role with M23.
Even after a peace deaal between Kinshasa and Kigali, violence has persisted in eastern Congo with both sides accusing each other of violations.