EU's Juncker pushes May for Brexit talks 'soon'

European Commission President Jean-Claude Juncker urged new British Prime Minister Theresa May to swiftly engage divorce talks with the European Union.

The outcome of the UK vote to leave the EU "has created a new situation which the United Kingdom and the European Union will have to address soon," Juncker said in a letter to May published on his Twitter account.

"I wish you every success in the task ahead," he added.

European Parliament President Martin Schulz also piled on the pressure as he congratulated May.

"Leadership issue settled, now I expect we work quickly to deliver certainty," he said.

EU president Donald Tusk meanwhile said he looked forward to a "fruitful working relationship" with the incoming May.

"I look forward... To welcoming you to the European Council" of European Union leaders, Tusk added in a brief letter.

May's first meeting with key EU leaders could be at the G20 summit in China on September 4, but her first encounter with all of the other 27 EU leaders will be at the next European Council summit on October 20-21.

Since Britons narrowly voted for Britain to leave the bloc in June 23 referendum, European leaders have asked London to quickly formalise its divorce but May has indicated she will not be rushed.

On a visit to Brussels today, US Treasury Secretary Jacob Lew urged Britain and the EU to remain "highly integrated" after Brexit.