European Council President Donald Tusk on Friday congratulated British Prime Minister Theresa May on her reappointment, underscoring that Brussels and London should press ahead with the Brexit talks.

"Our shared responsibility and urgent task now is to conduct the negotiations on the UK's withdrawal from the European Union in the best possible spirit, securing the least disruptive outcome for our citizens, businesses and countries after March 2019," Tusk said in his congratulation letter to May.

"The time frame set by Article 50 of the Treaty leaves us with no time to lose. I am fully committed to maintaining regular and close contact at our level to facilitate the work of our negotiators," he added. 

European Commission President Jean Claude-Juncker, also said earlier on Friday in Prague that the EU "can open negotiation tomorrow morning at 09.30."

"We are waiting for visitors coming from London. I hope that we will not experience a further delay in the conclusion of these negotiations," Juncker said at a joint press conference together with Bohuslav Sobotka, Prime Minister of the Czech Republic, and Rose Gottemoeller, NATO Deputy Secretary-General, following a high-level conference on defence and security.

"First, we have to agree on the divorce and exit modalities and then we have to envisage the architecture of our future relations. I do hope that the result of the elections will have no major impact on the negotiations we are desperately waiting for," he said.

May confirmed Friday afternoon she will form a Westminster government, helped by members of Northern Ireland's Democratic Unionist Party (DUP).

Speaking minutes after a 15-minute audience at Buckingham Palace with Queen Elizabeth, May announced her plan outside 10 Downing Street. 

She said the Conservatives and the DUP, "having enjoyed a strong relationship over many years", will work together.

The 318 seats won by the Conservatives in the election on Thursday, plus the 10 DUP seats will give May the majority she needs in the House of Commons.

In the election the Conservatives won most seats, but short of winning enough for an overall majority.