European Commission President Jean-Claude Juncker, in a flagship speech Wednesday, declared the "wind is back in Europe's sails" after last year's shock Brexit vote, an act he insisted Britain would regret.
In his annual State of the Union address, Juncker said the troubled bloc had become more united in the past 12 months and economic growth was picking up.
The EU should seize the momentum to deepen integration and sign new trade deals around the world, Juncker told the European Parliament.
Defying eurosceptics, the former Luxembourg premier called for more states to join the euro and the passport-free Schengen area and proposed a single EU president and finance minister.
"The wind is back in Europe's sails," Juncker told MEPs in the French city of Strasbourg, in a speech that mixed English, French and German.
"We have now a window of opportunity but it will not stay open forever. Let us make the most of the momentum, catch the wind in our sails."
Juncker did not utter the word "Brexit" until the very end of his 80-minute speech, saying that "we will regret it, but you will regret it too", earning jeers from British eurosceptics in the chamber.
"We will move forward -- because Brexit is not everything, because Brexit is not the future of Europe," the veteran politician added.
British eurosceptic leader Nigel Farage, who is a Euro-MP, responded to Juncker: "Thank God we're leaving -- you've learnt nothing from Brexit".
- Day-after-Brexit summit -
The 62-year-old Juncker has two years left in office as head of the EU's powerful executive to ensure that his legacy is not limited to the departure of one of the European Union's largest states.
He struck a far more optimistic tone than when he stood at the podium in September 2016.
Juncker had admitted then that "it was plain for all to see that our union was not in a good state, battered and bruised by a year that shook our very foundations."
With all 28 EU countries back in growth after years of economic crisis, and the rise of populism -- after Brexit and the election of US President Donald Trump -- apparently at bay for now, Juncker said there were reasons to be cheerful.
He called for the EU to hold a special summit, in Romania, the day after Britain's departure on March 29, 2019 to "throw off the bowlines, sail away from the harbour".
And while a future EU-UK trade deal remains a distant prospect, Juncker called on the bloc to seal trade agreements with Australia and New Zealand by the end of his mandate, and push for pacts with Mexico and South American countries.
Juncker called for an elected "single president" to lead the EU, merging his job as head of the European Commission, the bloc's executive arm, and the president of the European Council of member states, currently held by Donald Tusk.
That idea ran into immediate opposition from Denmark and the Netherlands, while an EU official said it was an "old, rather wide-ranging idea" that would require a change to the EU's treaties.
- Schengen, eurozone expansion -
Juncker's speech was full of calls for "more Europe", especially his suggestion that Bulgaria, Romania and Croatia should all finally become full members of the Schengen zone.
The eurozone should meanwhile be expanded beyond the 19 countries that currently use the single currency, in line with the EU's treaties that say all states must join the euro, he said.
Juncker furthermore backed French President Emmanuel Macron's call for a pan-European finance minister to help firefight future crises, although he was against Macron's proposal for a eurozone parliament.
The calls for more integration come despite the need to heal a deepening split with eastern European countries that resist such plans.
Juncker took a swipe at Poland and Hungary -- which have been at odds with Brussels over democratic standards -- saying EU countries should not be allowed to breach the "rule of law".
Turkey was also in his crosshairs as he ruled out EU membership "for the foreseeable future" because of President Recep Tayyip Erdogan's post-coup attempt crackdown, and urged Ankara to "let our journalists go" following the detention of several European reporters.
Juncker also attacked the "scandalous" conditions for migrants in Libya, with which the EU is working to try to stop Mediterranean crossings, and called for more solidarity with states like Italy that are on the frontline of Europe's migration crisis.
