Updated

European Union chief Donald Tusk appealed Thursday for calm as tensions soar between Brussels and London over negotiations on Britain's departure from the bloc.

"These negotiations are difficult enough as they are. If we start arguing before they even begin, they will become impossible," said EU Council President Tusk, who chairs summits of EU leaders.

He was speaking a day after British Prime Minister Theresa May accused some EU officials of actions that "have been deliberately timed to affect the result of the general election" on June 8.

May's remarks, made after the formal dissolution of the British parliament in preparation for the polls, were mostly aimed at drumming up support for her Conservative Party.

Tusk told reporters after talks with visiting Norwegian Prime Minister Erna Solberg: "The stakes are too high to let our emotions get out of hand. Because at stake are the daily lives and interests of millions of people."

The Brexit negotiations — which must be completed by March 30, 2019 — mark the first time a member has ever left the EU. The process is unprecedented and complicated, and the fresh delays caused by the snap elections in Britain are fueling tensions and uncertainty between London and the 27 nations that will remain.

"We must keep in mind that in order to succeed, we need today discretion, moderation, mutual respect and a maximum of good will," Tusk said.

Some of that good will appears to have evaporated since May met European Commission President Jean-Claude Juncker for a working dinner last week.

May's office said afterward that the meeting had been constructive. Juncker called it "excellent," but noted: "I have the impression sometimes that our British friends ... underestimate the technical difficulties we have to face."

A report in a German newspaper, citing anonymous Commission sources, quoted Juncker as saying he left the dinner "10 times more skeptical than I was before" that the talks can succeed.

May dismissed the report as "Brussels gossip."

Juncker's executive Commission, meanwhile, is said to be too busy to interfere in the British elections.

Chief spokesman Margaritis Schinas said Thursday that "we here in Brussels are rather busy with our policy work."

Schinas declined to directly say whether he thought May was using the Brexit dispute for political ends.