According to the report, the two brands are being studied as part of talks with an Obama administration task force assessing whether GM can be restructured without bankruptcy.
The report also indicated GM's Chevrolet, Cadillac and Buick brands are likely to be saved.
A decision is yet to be reached on what would happen to Pontiac or GMC should GM opt not to keep them with the possibility of a sell-off similar to that of Hummer, Saab and Saturn likely.
The report has been met with strong denial from a senior General Motors executive who says the report is "unfounded, unsubstantiated and untrue".
Company sales chief Mark LaNeve also denied rumors that GM plans to terminate the franchise agreements of poorly performing dealers before June 1 to accelerate its dealership consolidation campaign.
"The strategy we laid out for you in February is still the strategy," said Mr LaNeve. "Are we working it, tweaking it, examining every aspect of it? Yes, but nothing has changed with our strategy."
In the February report to the US Treasury Department, GM said it planned to go to market with four core brands: Chevrolet, Cadillac, Buick and GMC.
Pontiac would remain as a much smaller brand. GM is trying to sell Hummer, Saab and Saturn - and according to Mr LaNeve that is still very much the plan.
"They're not pressuring us to give up on anything," he said. "Buick and GMC are very profitable brands, and we have plans to make them even more profitable."