President Barack Obama could count on Britain to back him at nearly every turn during his first 7½ years in office. He knew British leaders had the global clout and shared perspective to be powerful U.S. partners.

But as Obama approaches the final months of his term, that sense of certainty has been shattered by the United Kingdom’s decision to leave the European Union and by the resignation of Prime Minister David Cameron, a close ally.

In his public reaction to the vote, Obama offered assurances that the two countries would remain “indispensable partners” and that the special relationship would survive. He said he respected Britain’s decision and that he was confident in an orderly transition from the EU.

Yet before the vote, Obama had warned in no uncertain terms of the consequences for Britain leaving the EU. He put the U.K. on notice it would become a low priority on trade while pushing back on the isolationist and anti-immigrant sentiments that have taken root in the U.S. and elsewhere and now seem to be tearing at Europe’s seams.

Vice President Joe Biden was blunter, saying that Britain’s exit was “not how we would have preferred it to be.”

The incongruence between Obama’s comments before and after the vote reflected the difficult spot in which the president finds himself.

With U.S. and global markets reeling, Obama wants to avoid the perception that U.K. relations will suffer. At the same time, playing down the significance of the exit could undermine his calls for Europe remaining integrated.

White House officials said they expect no immediate changes to the myriad areas where the U.S. and Britain are working together, including the British military’s involvement in the U.S.-led coalition fighting the Islamic State group. After all, Britain’s withdrawal from the EU could take years.

Still, there’s far less assurance that Britain and other European countries will reflexively take the U.S. side as new challenges arise.

“We instinctively turn to Europe for everything, and we’re going to turn and they’re just not going to be in a place to promote U.S. interests,” said Heather Conley, a Europe analyst at the Center for Strategic and International Studies in Washington. “The concern is that this is going to be so all-consuming that they’re not going to be able to take very difficult steps that are not popular.”

Defining the new U.K.-U.S. relationship will largely fall to the countries’ next leaders. Cameron’s resignation may not come until October, three months before the end of Obama’s term.

Early favorite to succeed Cameron is former London Mayor Boris Johnson, a forceful voice for leaving the EU who once suggested that Obama had an “ancestral dislike of the British Empire” due to his Kenyan roots.

American voters in November will likely be choosing between Democrat Hillary Clinton, who largely embraces Obama’s worldview, and Republican Donald Trump, who cheered Britain’s decision and predicted other European countries would follow suite.

In the meantime, Britain’s departure could alter the dynamics on nearly every issue where the U.S. promotes its interests overseas.

Though the U.K. will remain in NATO, the disarray in the EU raises the possibility of less unity on issues like Russia. With Britain’s support, Obama has been pushing to maintain sanctions on Moscow over its actions in Ukraine, but consensus has been hard to maintain as countries such as Germany and Italy, which trade heavily with Russia, lobby to lift them.

Britain’s record as a reliable partner isn’t unblemished. Obama has said Cameron’s failure to persuade Parliament to approve airstrikes against Syria’s government was a wake-up call that heavily influenced his decision to call off his own planned strikes in 2013. The White House was also frustrated that after leading the call for a NATO intervention in Libya in 2011, the U.K. seemed to lose focus as Libya descended into chaos.

Obama has maintained that a free trade deal being negotiated with the EU should be wrapped up by the end of the year, though that was doubtful even before the vote. Now the negotiations appear moribund.

Trade experts said the EU would be too consumed with figuring out its new economic situation to pursue a sweeping new treaty. U.S. Trade Representative Michael Froman argued Friday the deal is still worthwhile, but he acknowledged the U.S. was “evaluating the impact of the United Kingdom’s decision” on the talks. Obama had warned before the vote that if Britain pulled out, it would go to the “back of the queue” for a one-on-one trade deal with the U.S.

(AP)