German Chancellor Angela Merkel said she was looking forward to working together with Theresa May as world leaders congratulated her on becoming Britain's new prime minister.
"We will leave the British side to make their decisions now," Merkel's spokesman Steffen Seibert said Wednesday when asked what the German leader expected from May.
Belgian Prime Minister Charles Michel urged his new British counterpart to open talks on Brexit as soon as possible, as he joined other leaders in congratulating her on succeeding David Cameron.
Michel said May "will have to lead her country in challenging times and we wish her every success."
"We cannot afford a long period of uncertainty [over Brexit]. Clarity is in the interest of both Europe and the United Kingdom," he said.
"We expect the United Kingdom to activate Article 50 of the European Union's Lisbon Treaty in order to begin negotiations of the future relationship with the European Union," Michel said. "This should be done as quickly as possible."
European Commission President Jean-Claude Juncker sent his "warmest congratulations" to May after her appointment.
"I hope that we will have a chance to meet in the near future," Juncker said in a letter to May.
Juncker told May that Britain's decision to leave the EU had created a "new situation" which must be addressed "soon," adding that he looks forward to hearing her plans for Britain's relationship with the bloc.
EU President Donald Tusk also told May he looked forward to "a fruitful working relationship and to welcoming you to the European Council."
Russian President Vladimir Putin congratulated May and said he hoped to hold "constructive dialogue" with her, according to the Kremlin.
The United States expects a strong working relationship with May, White House spokesman Josh Earnest said, congratulating her on her new position.
The White House is confident that May will "pursue a course that is consistent" with President Barack Obama's views on the need for a smooth and orderly transition as Britain leaves the European Union, Earnest said.
Canadian Prime Minister Justin Trudeau congratulated May and thanked Cameron for his "service and dedication to the people of the United Kingdom, especially during times of economic uncertainty."