Soros, a liberal philanthropist, wrote in an article published by Project Syndicate that Europe needed to radically reinvent itself.

"Negotiating the separation with Britain will divert the EU's attention from its own existential crisis, and the talks are bound to last longer than the two years allotted to them," he said. "Five years seems more likely."

Soros said the EU should approach the Brexit negotiations in a "constructive spirit" and at the same time should make itself attractive again to people, especially younger generations.

British Prime Minister Theresa May, who faces elections on June 8, said earlier this week that Britain would leave the EU without an agreement if it was unable to achieve a satisfactory agreement with the bloc.

While stressing the need for a constructive attitude to talks with Britain, Soros said the EU had become an organization in which the euro zone constitutes the inner core and the other members are relegated to an inferior position.

"Replacing a 'multi-speed' Europe with a 'multi-track' Europe that allows member states a wider variety of democratic choices would have a far-reaching beneficial effect," he said.

"As it stands, member states want to reassert their sovereignty, rather than surrendering more of it."

He urged steps by the EU in three areas: territorial disintegration, exemplified by Brexit; the refugee crisis; and the lack of adequate economic growth.

But Soros said he was hopeful that after Emmanuel Macron, the only pro-European candidate, won presidential elections in France, and upcoming German elections could lead to a growing pro-Europe momentum which "may then be strong enough to overcome the biggest threat: a banking and migration crisis in Italy."

Soros, who has been portrayed by Hungarian Prime Minister Viktor Orban as a financial speculator who supported mass inflow of migrants into Europe, said he welcomed the EU's recent tough words on Hungary and Poland, two countries which critics say are on an authoritarian track.

"I admire the courageous way Hungarians have resisted the deception and corruption of the mafia state Orban has established, and I am encouraged by the European institutions' energetic response to the challenges emanating from Poland and Hungary," Soros said.

A Hungarian government spokesman said Soros had a clear political agenda, and the organizations funded by him were pursuing this.

"It has become quite clear now...that Soros wants to be the political opposition of the Hungarian government along with his organizations," Zoltan Kovacs said in a reply to Reuters.

(Reporting by Krisztina Than; Editing by Toby Chopra)