German Chancellor Angela Merkel (C), French President Francois Hollande (L) and Italian Prime Minister Matteo Renzi attend a news conference at the chancellery during discussions on the outcome of the Brexit in Berlin, Germany, June 27, 2016. [Photo/Agencies]

"There is no time to lose," Hollande said in a joint press conference with Merkel and Renzi.

He urged the British government to submit a formal exit application as soon as possible in order to start negotiations.

"Nothing is worse than uncertainty. Uncertainty often leads to irrational political behaviors, as well as irrational financial behaviors," he warned.

Renzi told the same press conference that while leaders were sad about the decision of the British people, "it is a good time for Europe to write new pages".

"I agree it must be done quickly, we must lose no time," he added.

The three leaders also said in a joint statement that they will propose at a summit starting Tuesday in Brussels to "launch a process based on a concrete timetable and precise commitments to find solutions to the challenges that arose from the result of the referendum in the United Kingdom, and to develop concrete solutions for a better future for the EU and its citizens".

They suggested that the remaining 27 member states of the EU should launch joint actions in securing external borders, strengthening the economy, and creating jobs for young people.