Europe is at least a decade behind the United States in exploring its shale resources, and no one is even certain how much oil and gas there is, much less how much can be recovered profitably.

“Our position hasn’t changed,” Total said in a statement. “We think it would be wrong for the country to close the dossier on shale gas without even knowing if there is any.”

Hess Oil France, which has a license for exploring for oil in the Paris basin, had been only about two days from beginning test-drilling in February when the government announced the halt, Mark R. Katrosh, the chief executive, said in an interview.

Mr. Katrosh, who noted that low levels of oil production had been taking place for decades in the Paris region, cited estimates that France held as many as 100 billion barrels of shale oil, of which perhaps 10 billion were recoverable.

Regarding the potential size of the resource, Mr. Katrosh said, “we’re all talking hypothetically right now. The country needs to debate and decide whether they see value in understanding what the potential resource is, and if they do, we’re one of the companies that’s willing to make the investment to better understand this and demonstrate that we can operate safely and respectfully of the environment.”

Industry officials remain optimistic that with public education and political will, economic logic will eventually carry the day. They acknowledge that Europe needs to modernize its regulatory system to adapt to the technology, and they say they expect to have to adapt to much stricter regulation than is the norm in the United States.

For the several hundred fracking opponents outside the National Assembly on Tuesday morning, no compromise is possible.