Haas, who runs the Newman Haas Racing team along with Paul Newman, resigned at the end of last month, CART said.
Said Haas: "My resignation should not be construed as a current lack of support for CART.
“I am committed to CART, that's the end of the discussion."
Added Chris Pook, CART's president and CEO: "We appreciate the time and effort he has devoted to CART, his vision and his support of the series, its shareholders and the sport."
A takeover proposal by the Open Wheel Racing Series will go before shareholders at the end of next month.
