"In order to assist in the funding of the Opel/ Vauxhall business until more permanent financing sources can be obtained, GM provided additional support of €650 million” on January 4, according to a statement sent to the US Securities and Exchange Commission (SEC).
"Specifically, GM is pre-paying the AOG Group (Adam Opel GmbH) for certain engineering services" that would normally come due in April and July, it added.
GM has decided to hang on to Opel/Vauxhall after initially agreeing to sell it off and needs €3.3 billion to finance the division's restructuring.
GM hopes to obtain €2.7 billion in aid from European countries where the carmakers have operations.
A plan drawn up by Nick Reilly, head of GM Europe and Opel, includes around 8,300 job cuts from a total workforce of nearly 50,000.
In November, GM paid Opel €600 million in order to reimburse a German loan that had kept the company on its feet.
GM itself has benefited from a US bailout that left Washington with a stake of more than 61 percent in what was once the world's biggest automaker.