(CNN) National Security Advisor Susan Rice on Sunday described how President Barack Obama and the White House prepared for, and then reacted to, the British referendum vote toward the end of last week.
During a talk at the Aspen Ideas Festival, Rice said the Obama administration developed contingency plans, coordinating with other major economies in Europe and Asia, including at last month's G7 summit in Japan. Treasury Secretary Jack Lew, the National Economic Council and the National Security Council all had contingency plans in place ahead of the vote.
The administration prepared for either outcome, including drafting presidential statements, but obviously more time was spent preparing for a "Leave" vote since that would have the greatest impact.
Obama was traveling most of Thursday afternoon, when results from Britain began emerging. Initially the White House was encouraged by tallies showing "Remain" in the lead. But as Obama sat down to dinner in San Francisco with tech entrepreneurs, it became clear that "Leave" was pulling ahead.
Before the vote even took place, the White House had made preparations for Obama to speak with British Prime Minister David Cameron after the result was known. Obama actually tried to connect with Cameron Thursday evening, but the time difference prevented them from speaking until early Friday morning, after the prime minister announced he was resigning.
Rice summed up the message Obama delivered to the British Prime Minister in one word: "Bummer."
Aside from the effects on bilateral ties, the two men also spoke in personal terms -- with Obama expressing appreciation for Cameron's friendship (Cameron once called himself Obama's "bro"). Rice said it was a "painful occasion" for Obama to watch "a partner that close experience a loss that profound."
As for the security implications of the Brexit, Rice said "there's a lot we don't know."
She said the current cooperation through NATO and on the counter-ISIS campaign would remain the same, describing immediate security concerns as "relatively few."