Analysts had expected the sale to fetch 9 billion euros (6.2 billion Pounds), valuing EDF at more than 60 billion euros.
But France's prime minister, Dominique de Villepin, has warned the deal could be in jeopardy over recent days.
"No decision has been taken," he told French TV channel France-2. "There are two things I want to see before I can envisage this recapitalization: that public service is guaranteed across the whole country on an equal basis. Secondly, I want a commitment that EDF will make the necessary investments."
His remarks followed a nationwide strike protesting against the government's privatisation drive, decried as a fire-sale of France's crown jewels to asset-strippers and foreign predators.
Mr de Villepin said he had "heard the message of the people".
The CGT union confederation said it was heartened by the apparent retreat. "The government is hesitating. It is now possible that it could abandon the privatisation altogether.
"The sale of EDF to private investors, even if only partial, is contrary to the interests of the nation and very dangerous for the future."
Critics have seized on a French finance ministry study warning that Europe could face "a California-style'' crisis if energy supply is left in private hands.
California suffered blackouts and a tenfold jump in electricity prices in early 2000. The debacle followed a botched deregulation of the sector in 1996, allowing Enron and other energy speculators to hold the state to ransom.
The study warned that big energy groups would try to limit over- capacity through mergers.
"This reinforces the risk that they could, in certain circumstances, orchestrate a shortage in order to force up prices," it said.
EDF has been counting on the sale to provide euros8billion for modernisation and to plug holes in its the balance sheet after rapid expansion across Europe.
The French state - already in breach of EU spending limits - lacks the funds to inject fresh capital, and is constrained by EU competition law.