EU leaders will use their meeting in the Romanian city of Sibiu on Thursday to take control of how events will unfold after the European elections in May, and hold their first discussion on the top EU jobs up for grabs after the vote - in particular, the EU Commission presidency.

The issue is likely to cause a clash between leaders and the EU parliament, which said it would only accept nominees for the EU commission presidency who ran as the 'Spitzenkandidaten' or lead candidates of their political families in the elections.

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EU leaders, on the other hand, insisted back in February 2018, that there is no automaticity between which candidate can build a majority in the parliament and the nomination by EU leaders.

Leaders said they cannot guarantee in advance that they will propose one of the lead candidates for the commission job.

The so-called Spitzenkandidaten procedure, introduced in 2014 by the European Parliament to have better control over who is appointed to head the main executive and legislative-proposing body in the EU, notably drives a wedge between the parliament and EU leaders, but also divides leaders themselves.

In 2014, it took three EU summits of leaders to agree on the Luxembourgish Jean-Claude Juncker, who ran as the centre-right European People's Party (EPP) back then - although British prime minister David Cameron and Hungarian PM Viktor Orban did not support his appointment.

The discussion will focus on the 'how' rather than the 'who'. Tusk will inform EU leaders on his intentions on "how to manage nominations" to the senior EU positions.

The EU council chief's aim is to get a swift agreement among EU leaders following the elections at the end of May.

"For Tusk, the question will be whether one can do it in less than three goes," an EU official said on Tuesday.

The official refused to confirm if EU leaders will meet on 28 May, two days after the election, for a first discussion of the results.

Another EU official said such a meeting on 28 May "sounds quite reasonable", but added that there might be the need for three or four meetings of leaders who should not be rushed into a decision.

EU leaders will also have to decide on Tusk's successor, the next EU's foreign affairs chief, and the president of the European Central Bank (ECB). A new president for the European Parliament will also have to take office.

Nominating senior figures is a complicated game for EU leaders, who will be trying to balance political parties, gender, and geography when deciding.

They also need to decide whether to enter into a clash with the parliament over the entire Spitzenkandidaten procedure.

French president Emmanuel Macron - who at the moment has no party presence in the parliament and therefore has no candidate to back - had opposed nominating the winning 'lead candidate' in the European elections, but has not put forward an alternative candidate.

Weber or else

The largest political alliance, the European People's Party (EPP) is expected to win the most seats in the election, even if they lose MEPs overall compared to five years ago. Bavarian Manfred Weber is leading their campaign.

The socialists have put forward commission vice president, the Dutch Frans Timmermans, the liberals have been promoting a team of candidates, while the Greens have been led by MEPs Ska Keller and Bas Eickhout.

No-one outside the spitzenkandidaten process has put themselves forward as candidates, although the EU's Brexit negotiator, Frenchman Michel Barnier, has been rumoured to be eying the position, making several recent speeches on the EU's future.

After the vote, Weber will have to build a majority coalition in the parliament, where nationalist and populist parties are expected to increase their representation. He will be looking at the socialists, the liberals - who have pledged to rebuild their parliamentary group with Macron's party - and the greens for that.

But there is little enthusiasm for the Bavarian politician among member states. Weber has been an MEP since 2004 but is still seen as inexperienced outside that bubble.

"Can you imagine Weber going up against Trump? He will eat Weber for breakfast," an EU source said, sharing concerns over Weber's preparedness for the top commission role.

The commission is in charge of trade talks in the EU, and its president might have to negotiate with US president Donald Trump over the next years.

Those close to Weber argue that the EPP group leader in the parliament has been systematically underestimated.

Nevertheless, the nine EPP politicians among the EU leaders are likely to back Weber, with the exception of Hungary's Viktor Orban.

On Monday, Weber lost the support of Orban, who had previously pledged to fight for the German candidate in the meetings of EU leaders.

Orban in a press conference in Budapest said Weber insulted Hungarians when Weber told ZDF television: "I would not take up office because I do not want to be elected by the far right ... I want to make clear that the centre is the dominant force, not the fringes."

The EPP suspended the Fidesz's membership of its political alliance last month, after long-standing disagreements over values and the rule of law - and Orban has since been edging closer to a possible far-right alliance.

Orban recently welcomed Italy's far-right deputy prime minister and interior minister Matteo Salvini in Budapest and on Monday he hosted Austrian vice chancellor Heinz-Christian Strache, leader of the far-right Freedom Party (FPO).

Weber, stuck between his party's more liberal stance and this nationalist platform, vowed to fight populism.

"In the year 2019, we will fight against those who want to destroy our Europe, the nationalists will be our enemies we fight against," Weber said at his campaign launch event in Athens last month.

Leaders will have a chance to decide on whom to nominate as commission president at their summit on 20-21 June. The new parliament is set to convene on 2 July.

Juncker, when asked on Tuesday if EU leaders will manage to derail the Spitzenkadidaten process, told reporters: "They tried to do it last time, and will not succeed this time."