The Russian-built Soyuz rocket that carried two satellites to Europe's Galileo navigation system as part of the Full Operational Capability (FOC) program. | Jody Amiet/AFP via Getty Images EU to UK: We won’t reimburse Galileo satellite funding Britain’s proposal to make Galileo a joint EU-UK program is a ‘big ask.’

There is "no basis" for the U.K.'s request to be reimbursed the €1 billion it contributed to the EU's Galileo satellite system if it is frozen out of the project post Brexit, according to a senior EU official, who added the bloc will not negotiate "under threat."

In what amounts to an initial response from Brussels to a concerted push by the British government to retain access to the system beyond the country's exit, the official said the European Commission is open to negotiation, but the U.K.'s position is "quite a big ask."

“I have the impression the U.K. thinks everything has to change on the EU side, so that everything remains the same on the U.K. side,” the official said, adding that London's demands violated the "legal requirements" agreed by member countries (including Britain) when Galileo was set up.

Earlier Thursday, the U.K. published a "technical note" — first reported Wednesday by POLITICO — expressing its desire to continue participating in the program and stating that it could pursue the creation of its own rival system if it did not receive adequate access to Galileo. The EU will allow participation on a "third country" basis, but that would restrict access to certain security-sensitive data.

Earlier this month, the EU's chief Brexit negotiator Michel Barnier told the EU Institute for Security Studies conference: "Third countries [and their companies] cannot participate in the development of security-sensitive matters."

The EU position has united Remainers and Leavers in Theresa May's often warring Cabinet on the question of future access to a system the U.K. regards as something it has part ownership of. The British government has set future access as a test case for the closeness of U.K.-EU security cooperation post Brexit.

Speaking at a briefing Thursday, the senior EU official said that the U.K.'s proposal to redraw the satellite program as a "joint EU-UK program" allowing privileged access after the country leaves the bloc would need to be put to the EU27 for discussion. London has made public demands for reimbursement of the money it has contributed to the program already. But the official indicated the suggestion — which has not been presented formally in negotiations — is a nonstarter that would amount to "backsliding" on the financial settlement it agreed in December.

"Theres a gap between whats happening in the negotiating room and whats coming out in the press. We’ll see whats possible within the negotiating framework, and whatevers outside the negotiating framework, we’ll speak to the member states and come back," the official said, adding "The EU doesn’t negotiate under threat."

The official specified that the U.K. is asking for privileged access to security-related data as well as manufacturing the security modules. The proposal would mean that the U.K. would "have the possibility to turn off the signal for the EU," and that in some circumstances, the U.K. could have "information that currently not all member states have," according to the official.

“We will also take this back to the member states and we will report back on how we will develop this,” the official said.

Asked whether shutting the U.K. out of security-related matters is a sign of distrust, the official responded: "That is not the issue. The EU is a rules-based system ... Why is that? Because 28 member states do not trust each other spontaneously ... They trust each other because there are remedies available. You don't trust each other when there are no remedies."

The official warned that the U.K. having access to sensitive information flowing through Galileo could threaten the EU's autonomy, "or to use a term dear to the U.K., it will breach the sovereignty of the EU."