EU-27 pledge to speak in 'one voice' after Brexit

"We reaffirm our belief that united, we are stronger in this increasingly unsettled and challenging world," the broad-brush statement said.

"We have been able to go thick and thin, we have proved this in numerous crises, […] we know the rest of the world is not asleep and we need to work hard to make it flourish," German chancellor Angela Merkel concluded to reporters after the meeting.

"One country on is own cannot solve the great global problems," Merkel added, saying leaders discussed defining the EU's role in the world, and that multilateral cooperation needs to be translated into the way the EU grapples with the big issues.

In the declaration, leaders said: "we will show each other solidarity in times of need and we will always stand together. We can and we will speak with one voice," adding that they will always look for joint solutions.

The declaration vows that the EU will act where it matters.

"I hope Europe will focus on a few important issues, like the internal market, migration, climate. Big on the big things, small on the small things. Europe where a deal is a deal, where the rule of law and democracy is upheld. That type of Europe," Dutch prime minister Mark Rutte, whose country has emerged as a key powerbroker in the bloc since the Brexit process, said ahead of the meeting.

Macron posits 'renaissance'

French president Emmanuel Macron said on Thursday that, at the European elections at the end of May, the EU faced a choice between projects to construct a future for the EU or a descent into nationalism.

"I think that now we need to move faster and with more determination ... on a European renaissance," Macron said, adding that his main goals for Europe were fighting climate change, a review of the Schengen passport-free zone to better protect borders, and building a new social and economic model for the bloc.

Climate change

In Sibiu, the leaders said in the declaration that Europe needs to be a global leader in upholding the rule-based international order and in the fight against climate change.

On Thursday, eight European countries - France, Belgium, Denmark, Luxembourg, Netherlands, Portugal, Spain, and Sweden - called for an ambitious strategy to tackle climate change and to spend 25 percent of the entire EU budget on fighting it.

They said the EU should have net-zero greenhouse gas emissions by 2050.

The Sibiu declaration also states that leaders will "protect our way of life, democracy and the rule of law", as the EU has already launched probes into Poland and Hungary for rolling back judicial independence and democratic freedoms, and recently Romania has been under scrutiny as well.

Defending the European way of life has been used as a trope by Hungary's anti-migration prime minister Viktor Orban. Orban and the lead candidate of their shared European People's Party, Manfred Weber, have also been at odds with each other in the past month.

10 Commandments

The joint statement - with 10 overarching commitments to reform and pledge allegiance - was labelled jokingly the "10 Commandments" for the next EU commission by some Brussels diplomats.

Leaders also discussed a strategic agenda, guidance for the EU institutions for the next five years, which they want to adopt in June.

The meeting in Sibiu was symbolically arranged for May 9 to mark the anniversary of Robert Schuman's 1950 call for the Coal and Steel Union that preceded today's EU. Its goal was to reinforce the EU's unity in the wake of the UK leaving the bloc, which has now been pushed back to October.

The discussions also touched upon Iran, after the EU has rejected Iran's decision to quit parts of the 2015 nuclear agreement a year after the US withdrew from the landmark accord.

Top jobs summit

Leaders also discussed top jobs in Brussels up for grab after the European elections, as they want to take control of political events unfolding after the vote.

EU council president Donald Tusk called for a special EU summit for 28 May to assess the results of the elections and added that he wants a decision by leaders on the EU commission president in June.

That may see national leaders' attempting to bypass the Spitzenkandidat process to pick the next Commission president, proposed by the parliament.

Spitzenkandidat process attacked

While EU leaders belonging to the centre-right European People's Party posed for a family photo with the party's lead candidate, Manfred Weber in Sibiu, others did not hide their dislike for the so-called Spitzenkandidaten - German for lead candidate - process.

"The Spitzenkandidat is a party organisation. Journalists and we speak about the Spitzenkandidaten, but ask my voters - they have no clue who is the lead candidate from any party," Xavier Bettel, Luxembourg's liberal PM said when arriving to the summit.

"The Spitzenkandidat candidature was a mistake since the beginning. It's not too late to ignore it," he added.

"I think it's a little bit out of democratic procedures and treaties," Lithuania's outspoken president Dalia Grybauskaite said.

But Weber sounded defiant.

"I have a clear mandate with 79 percent of the vote [of the party]. I think the whole EPP party would be seen as a ridiculous institution if we don't care anymore about the outcome of Helsinki [party congress]," he told reporters in Sibiu.