Washington - With a Tuesday deadline looming to submit proof to the government they can survive, General Motors and Chrysler were still locked in negotiations with unions and creditors to gain concessions.

Talks continued in Detroit Sunday, with the two companies pushing for billions of dollars of cost-cutting measures even as the Detroit News reported that Obama administration officials have not ruled out the possibility that the two companies may have to seek bankruptcy protection after all.

The News quoted an unnamed senior official as the source.

Obama officials have also apparently ruled out creation of a special "car czar" to manage the rescue efforts for the two companies, which have received more than 13 billion dollars in government loans.

If they cannot prove that they have made the changes to survive, GM and Chrysler will have to give the money back and will not get any more loans, according to the original terms of the agreement.

The decision to drop the "car czar" idea, reported by the News, the Washington Post and New York Times, is expected to be formally announced Monday.

Instead, oversight will be carried out by Treasury Secretary Tim Geithner and Larry Summers, director of the National Economic Council, the reports said. The two men will head an oversight team to be called the Presidential Task Force on Autos.

The companies will have until March 31 to make demonstrable progress in carrying out their restructuring plans that are to be laid out in Tuesday's reports. At that point, Geithner would have the final say about calling back the loans, the News reported.

US auto sales fell to the lowest in 27 years in January. Ford was the only one of the big Detroit three that did not seek urgent government help in December.

Chrysler, which has received 4 billion dollars, and GM, which has received 9.4 billion dollars, spent much of the weekend talking to the United Auto Workers union to gain concessions on retirement and health benefits.

Senior UAW official Ron Bloom would join the administration's car industry oversight team, the News and Bloomberg financial news service reported. (dpa)