"France is ready to provide the United States with all the aid it deems necessary," Fabius said in a statement.
The death toll across several states on the US eastern seaboard has risen to 42, with another death in Canada, and is expected to climb further as several people remained missing, officials said Tuesday.
Sandy had already killed at least 67 people – including a US national in Puerto Rico – as it swept through the Caribbean, meaning the overall toll from the storm is now 110.
Some eight million Americans remained without electricity on Tuesday.
Disaster estimating firm Eqecat forecast that the massive storm would affect more than 60 million Americans, a fifth of the country's population, and cause up to $20 billion (€15 billion) in damage.
"In the face of the devastating effects of Hurricane Sandy, I express my total solidarity with the American people who, after the Caribbean nations, are living through very difficult hours," said Fabius.
He appealed to French nationals in the disaster area to act with extreme caution and follow the advice of the US authorities.
Some 65,000 French people live in the northeastern United States, including 35,000 in New York, which bore the full brunt of the storm.
At least 18 people were killed in the city, mayor Michael Bloomberg said.