The future of Europe's space programme came under the spotlight in this southern Italian city Tuesday, where ministers discussed rival plans for a successor to the successful Ariane 5 launcher.

The 20-nation European Space Agency, meeting at ministerial level for the first time in four years, is staging two days of budget talks.

The meeting takes place against a backdrop of money worries, a fast-shifting satellite market and the growing strength of the US private sector in near-Earth space.

"This council (meeting) is crucial to sustain autonomous European access to Space..." France's Research Minister Genevieve Fioraso said in a speech prepared for the opening and sent to AFP.

In an interview with AFP last week, ESA Director General Jean-Jacques Dordain said he hoped members would back a three-year budget of 12 billion euros ($15 billion) but added he would be happy with "something around 10 billion euros."

It would mean a roughly stable budget compared with current levels, "but given the current situation, this is not small beer", he said.

One of the most crucial agenda items was deciding on a future generation of rocket launcher to replace the ageing Ariane 5.

The new rocket should provide more flexible launch options for the swiftly-changing satellite market.

France is pushing for a smaller, sleeker Ariane 6 launcher system, which would require about four billion euros, culminating in a maiden flight in 2021 if all goes well.

Germany wants a less ambitious option, an Ariane 5 ME (for "Midlife Evolution"), which would be readier sooner at a putative cost of two billion euros.

Weighing on many minds is not just belt-tightening but also the rise of the US private sector.

Last month, the US firm SpaceX sent an unmanned freighter, Dragon, to the International Space Station under a NASA initiative to delegate resupply missions to private corporations after the phaseout of the US space shuttle.

In an interview with the BBC in London on Monday, SpaceX boss Elon Musk said Ariane 5 "has no chance" of competing on cost terms with the firm's Falcon 9 and planned Falcon Heavy rockets.

"If I were in the position of Ariane, I would really push for an Ariane 6," he said.

SpaceX says it has an order book for more than 40 launches to resupply the ISS and place commercial and government satellites in orbit.