European Union legislators lashed out at U.S. President-elect Donald Trump on Wednesday for saying the British decision to leave the bloc would turn out great and predicting more countries would follow.

"It is insane," Guy Verhofstadt, the leader of the largest liberal group in the European Parliament, said, decrying what he saw as meddling in European politics and insisting on a much stronger EU reaction

"What would happen in the United States when European leaders would say 'Oh, we think California will break away,'" Verhofstadt asked rhetorically, adding that the EU's ambassador would immediately be summoned to Washington for chiding.

Manfred Weber, the leader of the biggest parliamentary group, the EPP Christian Democrats, said no one should underestimate the EU as an economic juggernaut on the world stage.

"I want to stress that the EU is as large as the U.S. in economic terms," Weber said.

Trump indicated in a weekend interview with two European newspapers that he was indifferent to whether the EU stays together or not. His position is a sharp break from the Obama administration, which encouraged British citizens to vote to remain in the bloc.

"I do think keeping it together is not gonna be as easy as a lot of people think," Trump said.

The British exit from the EU would "end up being a great thing," he said.

Combined with the stinging criticism Trump offered of German Chancellor Angela Merkel and European NATO allies, Trump's interview did not go down well in EU capitals.

"We must tell all those who are threatening Europeans, especially European businesses, that we, too, can ask tough questions to U.S. companies," said Weber, a German whose party is closely aligned with Merkel.

"If the U.S. is saying 'U.S. first,' then we are allowed to say 'Europe first,'" Weber said.

Both Weber and Verhofstadt, who leads the European Parliament's ALDE liberal group, said Trump presidency's should spur the EU into action and force it to display more unity.

However, EU President Donald Tusk said it was too soon to get excited.

"I am afraid we will have too many opportunities to comment on the words of U.S. president and no longer President-elect Trump," Tusk told the legislators Wednesday. "I am afraid it will be our daily work."