Jean-Claude Juncker, the President of the European Commission, will not seek re-election and will stand down in 2019, it has been reported.
Mr Junker said he will not seek a second term, despite becoming president in 2014 with the support of 26 of the 28 EU member states.
The former Prime Minister of Luxembourg also raised concerns that Britain will divide other member states by making different promises to each country during the negotiations.
The 62-year-old said looking back at 2014, when he became president, he had a good campaign but added "there will not be a second (campaign), because I will not run again".
"The other EU 27 don't know it yet, but the Brits know very well how they can tackle this," Juncker told German public radio Deutschlandfunk.
"They could promise country A this, country B that and country C something else and the end game is that there is not a united European front."
Britain is hoping to trigger Article 50 by the end of March, which will certainly provide substantial pressure for the European Union.
Three major countries in the bloc, France, Germany and the Netherlands, are all holding general elections this year, and anti-EU parties are expected to perform well.
