US president Barack Obama has made a 15-minute telephone call to Theresa May to congratulate her on becoming Prime Minister.
The tone of the call was "warm" and the two leaders discussed the importance of sustaining the special relationship between Britain and the US.
May told the president she hoped for "constructive and positive talks" with other EU leaders on the details of Brexit, according to the Prime Minister's spokeswoman.
May also had a 10 minute telephone conversation with European Commission president Jean Claude Juncker.
The call didn't go into the specifics of Brexit - but it was congratulatory in nature. And May told Juncker she wanted to see the appointment of Britain's new EU commissioner approved.
Juncker was speaking from Mongolia, where he is attending an EU-Asem summit.
May told Juncker she wanted to continue working closely with the commission on EU issues as well as British withdrawal from the union.
The Prime Minister explained that Britain would need some time to prepare for the negotiations on how Brexit would be achieved.
The call with Obama also featured discussions on how the US and Britain need to keep working together on global issues such as security, counter-terrorism, and intelligence sharing.
May also spoke to Italian prime minister Matteo Renzi and the First Minister of Northern Ireland Arlene Foster.