By Andrea Thomas

BERLIN--German Foreign Minister Sigmar Gabriel said Wednesday he expected negotiations over the U.K.'s exit from the European Union to be difficult, with the remaining members seeking to maintain good relations but also to defend the bloc's integration and internal market.

"The negotiations will certainly not be easy for both sides," said Mr. Gabriel. "Britain remains our neighbor, just as the European Union [is] for the British. We need each other. We should do everything to nurture good and friendly relations with London also in future."

He said the remaining 27 EU members were united in seeking a clear and detailed bargaining position for the Brexit talks over the next two years.

Germany's priority during the negotiations is to keep the rest of the bloc united and "not only preserve the great European integration achievements, but to enhance it further and prepare us for future storms," he said.

Earlier Wednesday, U.K. Prime Minister Theresa May formally announced the country's intention to quit the EU, setting in motion a two-year window for negotiations to extricate Britain from the bloc.

Martin Schaefer, a German foreign ministry spokesman, said the time frame was "tight" and the primary objective was to achieve an orderly Brexit that minimized uncertainties for citizens, businesses and EU states. He said many issues had to be settled, including the future status of EU citizens in the U.K. and vice-versa, as well as future trade and investment relations.

"Sometimes, you have to wonder whether London has really understood what kind of consequences this will have for the British economy," Mr. Schaefer said.

The first priority will be to agree on a divorce settlement for the U.K.--negotiations about future relations between the country and the EU can only start after that. "We have to start with the one, without being able to set rules for the other," Mr. Schaefer said.

German economic research institute Ifo said Wednesday that Europe's biggest economy had a great interest in the EU reaching a comprehensive free trade agreement with the U.K. once it left the bloc.

"Otherwise, Germany could become one main loser of Brexit," said Ifo President Clemens Fuest.

Britain is Germany's fifth-most important trade partner, with total trade volume reaching EUR122 billion ($132 billion) in 2016 and it was Germany's third-largest export market last year. Roughly 750,000 German jobs depend on trade with the U.K.

Write to Andrea Thomas at andrea.thomas@wsj.com

(END) Dow Jones Newswires

March 29, 2017 08:40 ET (12:40 GMT)