"Should the need arise, we will consider measures,'' he said on Monday.
Worries about GM's future have topped the news for months in Japan - where some of the world's automakers, including the Toyota Motor Corporation and Honda Motor Company, are located.
But the response has been relatively calm, attributed to a weakened GM expected to provide a growth opportunity for Japanese car-makers with their strength in smaller, fuel-efficient vehicles.
However, Japanese auto executives have tried to keep a relatively low profile about GM's woes because of a history of "Japan-bashing'' in the 1980s, when they were criticised as taking away American jobs with their exports to the United States.
Now, many Japanese cars are assembled in US factories by American employees.
Toyota surpassed GM as the world's biggest car-maker by annual vehicle sales last year.
But the decline in US vehicle sales since the global financial crisis hit last year has sent Toyota into its worst loss since its founding in 1937.
While GM struggles to penetrate the Japanese market, it is a leader in China - the world's second-biggest vehicle market - where its sales have been rising.