By Anna Peverieri and Mathieu Rosemain

PARIS (Reuters) -Eutelsat's shares soared on Friday after France said it would inject $1.55 billion into the debt-laden company, giving a boost to Europe's biggest hope for a satellite champion to rival Starlink.

French President Emmanuel Macron on Friday urged countries and companies as a matter of European sovereignty to invest in French satellite company Eutelsat.

Meanwhile, France and Britain are holding talks over the British government's possible participation in Eutelsat's rights issue, a source close to the matter said, confirming what a French government official said on Thursday.

An announcement could be made during Macron's scheduled state visit to the UK in early July, the source close to the matter added, speaking on condition of anonymity. Britain holds 10.9% of Eutelsat.

The company's shares were up 27.5% at 1235 GMT. Including Friday's rise, the stock has gained 59.61% year-to-date.

Other big Eutelsat shareholders, including Indian billionaire Sunil Mittal's Bharti Space, shipping company CMA CGM and Fonds Strategique de Participations, a long-term investment fund backed by French insurers, will subscribe to the capital increase, Eutelsat said on Thursday.

Musk has disrupted space-based communications with his rapidly growing constellation of low-Earth orbit, or LEO, satellites, amassing over six million Starlink users worldwide.

With about 650 active satellites, Eutelsat is much smaller. However, as the only other player with a major operational low-orbit constellation, it has attracted interest from European governments whose eagerness for non-U.S. alternatives derives from President Donald Trump's confrontational approach to their region.

"Eutelsat is the only non-American and non-Chinese player with these low-earth orbit constellations and such a wide range of services," Macron told reporters at the Paris Air Show.

"It's a matter of sovereignty," he said, adding: "and we hope that all French industrial financial partners will also subscribe ... and we also want to mobilise many other European and international partners."

Some analysts, however, were cautious about Eutelsat's prospects.

JP Morgan analysts said its leverage was expected to remain high in the medium term.

Eutelsat expects its debt level to fall to about three times annual earnings after the capital increase, down from four times today and a projected five times by mid-2026, JP Morgan added in a note to investors.

"We struggle to see this rights issue as sufficient to support what we would consider to be a truly competitive LEO strategy," it said.

Eutelsat's LEO satellite capability stems from its merger with OneWeb in 2023. At the time, it said the tie-up would lift the group's annual sales to $2 billion by 2027, with OneWeb's second generation of LEO satellites to be launched by the decade's end.

But Eutelsat has since said it needed more than three times the number of satellites previously thought, requiring up to 2.2 billion euros in financing.

($1 = 0.8686 euros)

(Additional reporting by Michel Rose, Clotaire Achi, Florence Loeve, Cassell Bryan-Low, Dominique Patton, Makini Brice, Benoit Van Overstraeten and Elisa Matinuzzi; Editing by Joe Bavier, Ingrid Melander, Barbara Lewis)