Britain’s pending divorce from the European Union brings into question the strength of its commitment to other alliances to which it contributes, namely NATO.

While the EU and NATO are distinct and separate organizations, membership overlaps and therefore the economic health and diplomatic relationships within the groups are interlinked. Senior U.S. and allied defense officials scrambled Friday morning to declare that Britain’s military obligations to its NATO allies will be fulfilled.

Secretary of Defense Ash Carter this morning called U.K. Defense Minister Michael Fallon to underscore that the military relationship between the two nations remains solid and should be unaffected by the vote. Carter called the “special relationship” between the United States and the United Kingdom “a bedrock of U.S. security and foreign policy.”

“He reaffirmed that those bonds endure after yesterday’s vote by the United Kingdom to exit the European Union. He also emphasized the United States’ unshakeable commitment to NATO, of which the United Kingdom is a vital member, and to the vision we share with our allies in the United Kingdom and other European nations,” Pentagon spokesman Peter Cook said Friday.  

“Secretary Carter welcomed Minister Fallon’s commitment to continuing the United Kingdom’s active and enduring role in global security issues, in particular its work within NATO and efforts to accelerate the lasting defeat of ISIL,” Cook said.

The U.K. and U.S. militaries have a lucrative partnership that includes heavy investment in the Lockheed Martin [LMT] F-35 Joint Strike Fighter program. Britain has committed to buying 138 F-35s. Though the economic fallout from the referendum is not yet understood, a perennial concern with the enormous F-35 program is whether partner nations will uphold their purchase commitments. The program’s cost schedule relies heavily on a ramp in production to begin in 2017 when international partners begin to take delivery of the jet.

“The U.K. is a key partner in the F-35, has been for some time,” Cook said. “They’re the biggest partner…and we have every confidence that they will continue to be a key partner in the F-35 program and we are not aware of any change in that relationship.”

“This is a bilateral arrangement, of course, with the United Kingdom,” Cook added. “It has not bearing on their status within the European Union and so we would expect their participation in the F-35 will continue.”

Cook was careful to point out that the decision to leave the EU was made by the British people and that Carter respects their decision.

“The secretary is confident that Britain remains a stalwart ally, a NATO ally, of course. The NATO alliance itself will be able to address this particular situation,” Cook said. “We remain very confident that the alliance, the core interests of the alliance, will continue to be served.”

Carter is fresh off a trip to NATO headquarters in Brussels where defense ministers met to discuss collective deterrence to a resurgent and aggressive Russia. NATO heads of state are set to meet in July in Warsaw, Poland, to formalize their strategy.

“The unity of NATO, of Europe, is an important thing,” a senior U.S. official said at the Brussels meeting. “Brexit, therefore, is a strategic issue.”

NATO Secretary General Jens Stoltenberg said in statement Friday that he is confident Britain’s commitment to the alliance will not be extinguished along with its EU membership.

“As it defines the next chapter in its relationship with the EU, I know that the United Kingdom’s position in NATO will remain unchanged,” Stoltenberg said. “The U.K. will remain a strong and committed NATO Ally, and will continue to play its leading role in our Alliance.”

“The Alliance remains committed to closer cooperation with the European Union,” he added. “At the Warsaw Summit in July, we will step up our cooperation, because together we are more effective in upholding our common values and keeping our nations safe.”