LONDON — Britain has warned the European Union it will build its own navigational satellite system if it is locked out of access to key defense-grade data from the Galileo network now being built by Brussels.

Defence Secretary Gavin Williamson became the second member of the government this month to threaten the EU. He said the country will respond to threats to deny it access to the military data needed to accurately target missiles by developing its own, rival system.

Britain could go it alone or team with other countries such as Japan, Australia and South Korea to build its own navigational satellite capabilities, Williamson said in an article for the Daily Telegraph.

“Defense scientists and the military experts have started work scoping out the possibilities of developing our own satellite system while we continue talks with the European Commission over our future role in Galileo. And we won’t rule out working with other nations,” he said.

The defense secretary also hinted Britain could adopt a similar effort to develop a new generation of fighter planes outside of the normal teaming with major European nations, further emphasizing the strains appearing between London and the EU on defense industry cooperation post Brexit — or Britain’s exit from the organization.

France and Germany announced progress toward launching a new fighter program at the recent Berlin Air Show with no mention of there being a place for Britain at this stage.

“I recently launched our new combat air strategy with industry to look at our next generation of fighter jets,” he said. “For us to succeed, we need to be ambitious and imaginative. That means exploring all the options and not just thinking about collaborating with traditional partners such as France or Germany but turning to new markets.”

Talking about the satellite system, Williamson said: “We have the expertise, the technical know-how and, crucially, the will to succeed.”

Britain has supplied much of the encryption and other know-how for Galileo.

The British are in negotiation with Brussels about their future relationship in the Galileo program in the wake of Brexit. The threat to build its own system is part of negotiations between the two sides. As things stand, only EU members would have access to the crucial military-grade data from Galileo.

A support facility capable of receiving military data from Galileo has already been moved from England to Madrid, Spain, and British companies have recently been locked out of further Galileo contracts.

The full network of some 30 Galileo satellites is expected to be operational around 2021.

For years Britain has relied on U.S. GPS for its military data. Russia and China also have navigational systems in orbit.

Britain has spent about £1.2 billion (U.S. $1.5 billion) as its contribution to building the nearly £9 billion satellite system, and industry here has received a substantial number of Galileo contracts in return.

The Financial Times recently reported the British were looking at whether they could recoup some of the money if Brussels barred access to the military data post Brexit.

British Business, Energy and Industrial Strategy Secretary Greg Clark recently delivered a similar message to Williamson about going it alone.

“The U.K.’s preference is to remain in Galileo as part of a strong security partnership with Europe. If Galileo no longer meets our security requirements and U.K. industry cannot compete on a fair basis, it is logical to look at alternatives,” he told the BBC.

The British have had a military space strategy waiting to be unfurled for several months, and its position on a Galileo replacement and wider issues like the Skynet 6 communications satellite systems could get an airing at a defense space conference being held in London later this month.

Defence Procurement Minister Guto Bebb and the chief of the Air Force, Air Marshal Stephen Hillier, are among the expected speakers at the Air Power Association event.

Andrew Chuter is the United Kingdom correspondent for Defense News.

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