After several delays including a last-minute postponement on Monday, the rocket carrying a French military satellite launched from Europe's spaceport in Kourou, French Guiana just before 1:30 pm local time (1630 GMT).

The high-profile mission comes as Europe seeks to strengthen its defences amid doubts it can still rely on the United States as a security partner under new US President Donald Trump.

A successful mission would mean that Europe can independently put large satellites into orbit for the first time since Russia pulled its heavy Soyuz rockets after invading Ukraine in 2022.

The launch was progressing normally, with the main stage separating from the rocket, according to an online broadcast from its operator, French firm Arianespace.

The rocket is expected to reach orbit an hour and six minutes after launch.

A previous attempt on Monday was called off just 30 minutes before launching due to a dysfunctional valve on one of the refuelling pipes, Arianespace said.

Previous attempts to launch the mission in December and February were also scrubbed.

Postponed launches are common for new rockets. The latest test flight of the world's biggest rocket, SpaceX's Starship, is also scheduled for launch later Thursday after a last-minute postponement on Monday.

- 'Europe must ensure its own security' -

Ariane 6 was initially scheduled to have its first flight in 2020, but repeated delays meant the rocket did not blast off for the first time until July last year.

Its first commercial mission is to put the CSO-3 satellite into orbit at an altitude of around 800 kilometres (500 miles) above Earth.

CSO-3 has been waiting since 2022 to complete a network of three French military imaging satellites, with the first two launched in 2018 and 2020 on Soyuz rockets.

Europe has just 10 military satellites -- five French and five Italian -- compared to "hundreds" for the United States and China, French General Philippe Steininger said.

"Europe must ensure its own security," the European Space Agency's space transportation director Toni Tolker-Nielsen said in Kourou earlier this week.

He called for the number of annual Ariane 6 launches to increase to 12, compared to the five planned for this year.

The European space industry has struggled to remain competitive with Elon Musk's SpaceX, which has become increasingly dominant when it comes to launching satellites.

And SpaceX is only expected to become more central to US space efforts now that the billionaire Musk has become a prominent advisor to Trump.

- 'Important step' -

Europe recently found itself without a way to independently launch missions into space due to the Ariane 6 delays.

Its predecessor Ariane 5 retired in 2023, Russia pulled its Soyuz rockets and an accident grounded the smaller Vega-C launcher for two years.

But with Vega-C resuming flights in December and Ariane 6's first commercial launch, European space efforts are hoping to turn a page on the crisis.

Given the military role of the satellite, heavy security was deployed at the spaceport on the northern coast of South America, with French fighter jets deployed to patrol the surrounding skies.

Arnaud Prost, a French pilot who is also a reserve astronaut for the European Space Agency, learned that Monday's launch was scrubbed while he was flying a surveillance plane above the launchpad.

A successful Ariane 6 launch would be "an important step for the independence of France and Europe's access to space," he told AFP.

"At the moment, Europe needs to find projects that bring us together," he said.

"Space exploration is a unique opportunity to do this."

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