PARIS — The French and German governments remain so far apart on a future space-launch policy for Europe that officials are now privately talking about canceling a December conference of European space ministers or stripping it of concrete decisions.

The basic division remains despite the German government’s alignment with the French view that Europe needs a lower-cost rocket to maintain its viability in the commercial market — which in turn provides European governments with a viable launch industry.

Despite the consensus over the longer term, the two sides remain split on whether European Space Agency governments should spend 1.2 billion euros ($1.6 billion) to complete work on a new upper stage for the existing Ariane 5 rocket, which could fly in 2018-2019, or abandon the upgrade to focus spending on a new Ariane 6 rocket, whose development would cost upwards of 3 billion euros over 7-8 years.

Each side has its arguments.

Germany says completing the Ariane 5 ME vehicle, with a more powerful and restartable upper stage, would give the Arianespace launch consortium a superior weapon in the commercial market before the end of the decade.

The problem: Ariane 5 ME likely will cost as much to launch as the current Ariane 5 ECA rocket, or around 140 million euros, thus requiring continued ESA cash injections of around 100 million euros per year to balance Arianespace’s books.

The French argument is that the Ariane 5 ME money could be better spent on Ariane 6, especially if there is a consensus that this rocket should be in service around 2022.

ESA and the French space agency, CNES, have been working on an Ariane 6 design since the last ESA ministerial conference in November 2012. But this design, with two solid-propellant stages topped by a cryogenic stage, faced criticism from the commercial market and from Germany, which said its industry would not have much of a place in the rocket’s construction.

A mid-June proposal by Ariane 5 prime contractor Airbus Defence and Space and rocket motor maker Safran, celebrated by French President Francois Hollande, provided the final blow to the ESA design, officials said.

The current Ariane 6 design being considered is a solid-fueled first stage with cryogenic second and third stages, bolstered by one or two pairs of solid-fueled strap-on boosters.

The Airbus-Safran proposal says this vehicle could be built and launched for 80 million euros assuming 10 launches per year. For lighter payloads of the sort often launched by European governments, the core vehicle would use two strap-on boosters in a version called Ariane 62.

A heavier Ariane 64 variant would be used to orbit commercial payloads weighing up to 11,000 kilograms. The core would be augmented with four of the same strap-on boosters, each carrying 120,000 kilograms of solid propellant.

ESA and its principal member states have agreed that whatever solution is selected, the agency’s total annual spending on launch vehicles — including the Vega small-satellite launcher and any costs associated with Ariane 5 operations — should not exceed 800 million euros per year.

Ariane 5 ME and Ariane 6 cannot both be fitted into this spending corridor; ESA governments must delay or cancel one of them.

Ariane 5 ME supporters say they believe they can cut the vehicle’s recurring launch cost by 10 percent, enough to make its operations on the commercial market more profitable and to do away with the annual government support payments. The vehicle’s skeptics doubt whether this will be the case.

Ariane 6 skeptics say the 80 million-euro cost per launch, assuming 10 launches per year, will be a stretch for the industrial team. And 80 million euros is already more than the 70 million-euro target that ESA and CNES, had set for their earlier Ariane 6 design.

Many European government officials, at ESA and at the national space agencies, notably in France and Germany, agreed to forgo their summer vacations to meet weekly to find a solution. They met again Sept. 4 and will reconvene with an important date of Sept. 17.

Several European space ministers will meet Sept. 23 in Zurich to determine whether there is hope for a common policy in time for the ministerial conference set for Dec. 2 in Luxembourg. If the answer is no, they will have the option of canceling the Dec. 2 meeting, or maintaining the date but limiting the conference to a general statement about Europe’s future launch-vehicle policy, with costs, dates and design details to be decided later.

As has been the case for a year, discussion in Europe about continuing as a partner with the United States on the international space station to 2020 and beyond has been put on ice pending a decision on launcher policy.