Addressing lawmakers at the European Parliament, Commission President Jean-Claude Juncker said the EU is "bouncing back" after a tough decade that's seen much of the 28-country mired in an economic crisis and Britain vote to leave.
Mr Juncker said: "This will be a very sad and tragic moment in our history".
The European Commission President used his speech to call for a special summit of an EU of 27 member states on the 30th March 2019, the day after Britain will formally leave the EU.
"Although the whole Brexit deal will have to be approved by the UK Parliament, by EU national governments and by the European Parliament, it is highly unlikely that these issues will be a sticking point. However, the European Parliament has made it clear that, whatever the outcome of the negotiations on the future European Union-United Kingdom relationship, they can not involve any trade-off between internal and external security, on the one hand, and the future economic relationship, on the other hand".
He said: "I think we are going to find ourselves running into quite a lot more difficulties over the next few years or so as the negotiations proceed".
"Turkey has been moving away from the European Union in leaps and bounds", he said, criticizing Turkish President Recep Tayyip Erdogan and his government for arresting journalists and branding EU leaders "fascists and Nazis".
"And that rules out membership for Turkey for the foreseeable future".More news: Armie Hammer, Amber Tamblyn call out James Woods for hypocritical tweet
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His latest comments are a barometer of the political mood in European Union national capitals regarding Erdogan, whose support for a 2016 pact stemming a wave of Mideastern refugees into the bloc its leaders are still counting on.
He backs that argument by calling for all European Union states to adopt the euro and offering technical and financial help for countries that need it.
Addressing unease in Europe about such deals, Juncker stressed their power to create jobs and impose European Union standards in areas such as the environment on trading partners.
Juncker however insisted that Europe remained open for business and would seek to complete trade deals with Australia and New Zealand by the end of his mandate.
"Europe would be easier to understand if one captain was steering the ship", he argued.
He did not give more details of the new tasks the EMF could take on, saying only the Commission would make a proposal on that, as well as the prerogatives of a European finance minister, in December.
Chubb has said that it will continue to have a significant presence in London post-Brexit, as well having offices across the United Kingdom and the Europe Union.