BERLIN — The United Kingdom has walked away from negotiations over its post-Brexit involvement in the European Union‘s Galileo global navigation satellite system (GNSS).

Instead of using Galileo‘s military-grade signal, Prime Minister Theresa May announced Nov. 30 that the U.K. will explore building its own GNSS.

Expected to reachfull operational capacity in the 2020s, Galileo is the EU‘s answer to navigation systems like the United States‘GPS. Galileo‘s Public Regulated Service (PRS) — a secure and encrypted signal used for defense and government purposes — is meant to be restricted to EU members.

That means that after Brexit, British companies would not be able to bid for contracts involved in developing and maintaining PRS, and the U.K. would have to work out a deal with the EU even to become a passive user of the military-grade signal, unless another arrangement was reached.

May blamed the end of the negotiations on the European Commission‘s “decision to bar the UK from being fully involved in developing all aspects of Galileo.”

“I cannot let our Armed Services depend on a system we cannot be sure of,” May said in a statement. “That would not be in our national interest. And as a global player with world-class engineers and steadfast allies around the world we are not short of options.”

Sam Gyimah, the U.K.‘s universities and science minister, resigned from his post in protest, calling Galileo “only a foretaste of what’s to come” under the Brexit deal.

“Having surrendered our voice, our vote and our veto, we will have to rely on the ‘best endeavours’ of the EU to strike a final agreement that works in our national interest,” Gyimah wrote in a long statement posted to his Facebook page. “As Minister with the responsibility for space technology I have seen firsthand the EU stack the deck against us time and time again, even while the ink was drying on the transition deal. Galileo is a clarion call that it will be ‘EU first,’ and to think otherwise—whether you are a leaver or remainer—is at best incredibly naive.”

Some space policy experts said it‘s not out of the question for a deal over Galileo access to be reached in the future.

“There‘s no reason Britain should have given up trying to gain access to PRS as a passive user, in the same way that the United States‘military allies use GPS for the military signal,” said Bleddyn Bowen,a lecturer in international relations at the University of Leicester. “The EU wasn‘t ruling out that Britain could use PRS as a passive third-party in the same way we do with GPS.”

Similarly, Sa’id Mosteshar, of the London Institute of Space Policy and Law, said that the armed forces of non-EU members can gain access to the signal under asecurity agreement with the EU. “It was open to the U.K. to reach such an agreement and it is surprising that it has decided not to do so,” Mosteshar said.

Bowen added that the Brexit process is in “quite a moment of flux” and he thought the Galileo issue could be picked up again in the future.

“The declaration from Theresa May was basically, I think, to make Britain look like it had agency in the matter rather than cutting off its nose to spite its face,” Bowen said. “It is really more political theater as May is now fighting at this crunch moment in the Brexit process because Parliament may be undertaking a contempt of Parliament motion against her.”

Earlier this year U.K. space officials had floated the idea that they could partner with another country, such as Australia, to build a new GNSS. In August, the British government announced it would spend92 million pounds ($117 million) from a “Brexit readiness fund” to study the prospects for building an independent alternative to Galileo.

“The cost of developing a national replacement has been estimated to be in the region of £3 billion to £5 billion ($3.8 billion to $6.3 billion) and this is a significant expenditure when considering that the current U.K. space budget is only £370 million ($470 million) per year with the majority of that going to fulfill U.K. commitments to ESA,” said Christopher Newman, a professor of space law and policy at Northumbria University.

Newman added that it wasn‘t clear where the budget for such an expensive project would come from.

“Either it wipes out the existing U.K. space budget for 10 years,” he told SpaceNews, “or, as is more likely, it is additional defense expenditure that others will argue could be much more effectively be spent elsewhere.”

Though Galileo is an EU program, it is operated by the European Space Agency (ESA), a separate body which the U.K. will remain part of after Brexit. Newman said the Galileo negotiations may have damaged the U.K.’s ability “to maintain good relationships across ESA.”

“The U.K.’s commitments to working collaboratively in space with European partners contrasts sharply with some of the bellicose rhetoric that has been seen in respect of the Galileo program,” Newman said. “This will not have gone unnoticed by potential collaborators when further, lucrative space-based projects are put out for tender by the EU.”

The Financial Times reported that the British government is expected to seek compensation for the 1.2 billion pounds ($1.5 billion) it has invested in Galileo’s development.