DuPont President Ellen Kullman will leave the board of directors at General Motors Corp., as the auto maker appeals for $18 billion in loans and credit from the U.S. government to stave off bankruptcy and help it through the economic downturn.

Kullman will resign her board seat, effective immediately, to focus on her new responsibilities at El DuPont de Nemours & Co., GM says.

Kullman, 52, was appointed president and a board member of the science and technology company in September. She takes over as its CEO in January.

“I have been proud to serve on GM’s board for four years,” Kullman says in a statement released today. “GM has made important advancements across a number of fronts, and I wish the GM team continued success as they work to overcome the current challenges.”

Addressing a possible replacement for Kullman, GM says it always assesses potential candidates but has not made any decisions on a replacement. Kullman’s departure would leave GM with 13 board members, including Chairman and CEO Rick Wagoner.

Kullman served on GM’s Audit Committee and Investment Funds Committee. The auto maker says it has no immediate plans to replace her on those committees.

Although the House of Representatives passed a bill last night that would provide GM with a first installment of low-interest direct loans, the auto maker’s appeal remained in flux late into the afternoon due to strong opposition from leading Republicans in the Senate.