The Obama administration has no timetable for the government to sell its equity stake in a revamped General Motors Corp. (GM), a senior Obama adviser said Monday, raising the prospect of multi-year U.S. ownership of the auto maker.

The decision on when to beginning selling the government's shares will be driven largely by factors beyond the government's control, such as market conditions, the health of the broader economy and the company's performance, said Steven Rattner, a member of President Barack Obama's auto industry task force.

The goal is to keep government ownership brief but to also wait until a sale of shares will provide a maximum return to U.S. taxpayers, who will have invested $50 billion in the auto maker, Rattner said.

Rattner, briefing reporters Monday, said the U.S. government will likely divest itself of GM shares through a series of sales rather than a single off-load. The transactions will be coordinated with the Canadian and Ontario governments, which are also set to take ownership stakes in GM, Rattner said.

But when and how those transactions will take place haven't been determined, he said.

"All of that will have to be evaluated and judged as time goes on," Rattner said.

Under a plan outlined by Obama and GM Monday, the government will hold a 60% ownership stake in the company once it emerges from Chapter 11 bankruptcy.

-By Josh Mitchell, Dow Jones Newswires; 202-862-6637; joshua.mitchell@dowjones.com