The President spoke by phone today with Prime Minister of the United Kingdom Theresa May to congratulate her on her new office. President Obama emphasized that the special relationship between the United States and the United Kingdom remains strong and will endure and that he looks forward to building a close working relationship with Prime Minister May. The President also offered his full support for the Prime Minister's efforts to lead the United Kingdom through a smooth, orderly, and transparent negotiation over its exit from the European Union.
Barack Obama, Readout of the President's Call With Prime Minister Theresa May of the United Kingdom Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/317982