BERLIN (Reuters) - German Foreign Minister Frank-Walter Steinmeier said Britain's decision to leave the European Union would have long-term consequences that were still difficult to estimate, and said both sides needed new, fair and binding rules for their future ties.

Steinmeier told over 1,000 German diplomats and business executives at a foreign ministry conference that it was in Britain's interests to start the process quickly given economic effects that were already becoming evident.

(Reporting by Andrea Shalal; Editing by Madeline Chambers)