Reuters newsagency quotes the respected British business newspaper as saying an investor will be asked to pay at least 500 million euro, or US$652 million in equity, but GM will realise no financial gain as the money will be injected directly into Opel.
GM is also prepared to unload Saab, its Swedish premium brand that filed for creditor protection in February, for as little as nothing in order to divest the brand, the Financial Times report said.
GM, which has lost more than US$82 billion since 2005, has received $13.4 billion in US federal loans and is seeking more than US$16 billion in additional government aid.
The White-House appointed task force has given GM 60 days to come up with a restructuring plan that cuts costs and debt levels more deeply than the carmaker had planned.
By that point, officials have promised a decision on whether to support GM's turnaround as a much smaller auto company or whether to put it through a bankruptcy process intended to shed debt and laggard assets.
GM Chief Executive Fritz Henderson has already said the carmaker was in talks with more than six financial and industrial groups about acquiring a stake in its European arm.
The Financial Times said Commerzbank, GM's advisers on Opel, last week sent out an offer document for the German brand.
Italy's Fiat and SAIC, GM's main joint venture partner in China, have both denied interest in buying Opel/Vauxhall.
The Financial Times also said GM's European unit is engaged in "aggressive" contingency planning to protect itself in case the company files for bankruptcy in the United States, citing a person familiar with GM's plans.
Options under consideration at GM are said to include putting financing in place for its international holdings ahead of a bankruptcy filing, and seeking debtor in possession financing from the US government for the international operations after a Chapter 11 filing, the report said.