US automaker General Motors must undergo a "substantially more aggressive restructuring" if it is to have a long-term future, the White House said yesterday in a tough review.

A task force set up by President Barack Obama found the company's current plan to shake-up its ailing business and qualify for more government loans "is not viable and will need to be restructured substantially."

"It is strongly believed, however, that such a substantial restructuring will lead to a viable GM," the task force said in a report, warning such a radical overhaul of the business will take many years to complete.

"GM's plan is based on a number of assumptions that will be very challenging to meet without a more dramatic restructuring in which many of its planned changes are accelerated," the report found.

The struggling automaker submitted its restructuring plan to the US Treasury as part of a request for an additional $16.6 billion in US government loans on top of the $13.4 billion approved in December.

But the White House highlighted some of the challenges facing the company:

Falling market share: "GM has been losing market share to its competitors for decades, yet its plan assumes only a very moderate decline, despite reducing fleet sales and shuttering brands that represent 1.8 percent of its current market share."

Price: The plan assumes improvement in net price realization despite a severely distressed market

Brands: GM is burdened with underperforming brands and too many dealers, "which will create a drag on the overall brand equity of GM," a problem which is not dealt with aggressively enough in its bailout plan.

Products: The company gets too great a share of its profits from trucks and SUVs, amid a market shift towards smaller cars.

Cash Flow: To meet its liabilities, which will reach six billion dollars in 2013 to 2014, GM will need to sell an extra 900,000 cars a year "creating a difficult burden that leaves it fighting to maximize volume rather than return on investment."

While General Motors had made progress in past years to turn the company around, progress had been far too slow, the report said.

"However, because of GM's scale, franchise and progress to date, we believe that there could be a viable business within GM if the company and its stakeholders engage in a substantially more aggressive restructuring plan," it added.

GM has repeatedly warned that it would likely end up being liquidated if it was forced into bankruptcy protection because consumers would be unwilling to buy its vehicles.

The company expects to reduce its operating costs significantly in the coming months as it completes its radical downsising, which includes plans to slash its global workforce by 47,000 people and eliminate a number of brands.

It is also working to restructure its debt and is in negotiations with its main US union to lower labour costs and pay up to half of a $20 billion retiree health care liability in stock instead of cash.

Deals on both matters had to be reached by today, according to the terms of emergency loans granted by the US Treasury department.

But the White House said Monday that the conditions of the loan agreement had not been met.

It also warned that the company's European business units have been seeking extra funds beyond those requested from the Treasury.