PARIS — A group including the world’s largest commercial satellite fleet operators has written the European Space Agency urging that it approve a new-generation Ariane 6 in time for a first launch in 2019 or face relegating the European rocket to commercial also-ran status.

The letter to ESA Director Jean-Jacques Dordain makes clear that these fleet operators have a ho-hum view of the Ariane 5 ME vehicle that ESA governments are weighing alongside a new-generation Ariane 6.

Given the advent of electric propulsion and the dramatic launch-cost reduction offered by Space Exploration Technologies Corp., the operators say, the new Ariane 6 needs to be in service by 2019 or face the risk that Europe’s Arianespace launch consortium will be permanently sidelined.

The letter was signed by six members of the European Satellite Operators Association. Signatories included the chief executives of Intelsat, SES, Eutelsat, Inmarsat, Hispasat and HellasSat.

ESA governments are debating whether to spend 1.2 billion euros ($1.6 billion) to complete work on the Ariane 5 ME rocket, which uses a new, restartable upper stage that will also serve Ariane 6. The Ariane 5 ME could be in service by 2018.

Given their budget constraints, it appears unlikely that ESA governments will be able to finance both Ariane 5 ME and full-scale development of Ariane 6, whose costs have been estimated at up to 3 billion euros.

Michel de Rosen, chief executive of Paris-based Eutelsat, punctuated the companies’ sentiments here Sept. 9 during the World Satellite Business Week conference organized by Euroconsult.

In a briefing, de Rosen said Eutelsat had agreed to let Arianespace launch Eutelsat’s 172B satellite — the first all-electric satellite ordered by Eutelsat — even though a SpaceX launch would have been less expensive.

De Rosen said Evry, France-based Arianespace had agreed to cost reductions such that the difference between the SpaceX and Arianespace prices was “marginal.”

De Rosen presented the no-bid launcher selection as a kind of European duty to support European hardware manufacturers. He said Eutelsat had informally offered Arianespace the possibility of launching a Eutelsat satellite on the inaugural Ariane 6 rocket, so long as the launch occurred no later than 2019. No contract has been signed, however, and de Rosen characterized the offer as a way of expressing support for Ariane 6 more than as a contractual commitment.

ESA governments have said their next rocket’s principal mission should be launching European government satellites — unlike the current Ariane 5, a heavy-lift vehicle that is ill-adapted to most European government missions and generates 80 percent of its revenue from the commercial market.

The operators’ letter acknowledges this, but reminds ESA that without the commercial market, the Ariane business would be a shadow of its current self.

Peter B. de Selding was the Paris bureau chief for SpaceNews.