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The success of the 31-year-old, who is poised to become the continent’s youngest leader, has been tentatively welcomed by the European Union’s leading figures. But they have warned “Wunderwuzzi” (boy wonder) against forming a coalition with the far-right. Mr Kurz, whose Austrian People’s Party topped the polls after promising a tough line on immigration, is still weighing up a coalition with the country’s far-right Freedom Party (FPO).

GETTY Jean-Claude Juncker and Sebastian Kurz

I wish you great success in establishing a stable, pro-European government Jean-Claude Juncker

In a letter of congratulations, Mr Juncker wished him success in forming a “stable, pro-European government”. But the European Commission president also warned Mr Kurz about attaching himself to the Eurosceptic party founded by former Nazis. He has made no secret of his contempt for the FPO in the past. In an interview with Le Monde in 2016 he said: "I do not like them. With these right-wing populists it is neither possible to debate nor having a dialogue.” Mr Juncker has stopped short of pressing Mr Kurz to shun the FPO, as EU leaders did when Chancellor Wolfgang Schuessel formed a coalition with the party then led by Joerg Haider in 2000. But he said he was looking forward to the creation of an EU-supporting government with the leader-in-waiting.

GETTY Sebastian Kurz is poised tobecome the new leader of Austria

In his letter to Mr Kurz, Mr Juncker wrote: “I would like to warmly congratulate you on your party winning the most votes during the Austrian parliamentary election. “There will now be challenges Austria and you, yourself will have to face. “Soon, Austria will play an outstanding role being the presidency of the council of the European Union. “Under Austria's responsibility a number of important decisions regarding the European Union will have to be made. “Therefore I wish you great success building a stabile and pro-European Government and I look forward to working together in the future.”

GETTY European Commission president Jean-Claude Juncker

Mr Kurz has promised a “new political culture” but has yet to reveal what shape he wants his new government to take amid intense closed-door negotiations. He has described himself as pro-Brussels and even described last Sunday’s election result as a “clear victory for the European Union”. But despite the pro-EU pledge, he has previously spoken about joining forces with the FPO, which would see Austria join Poland and Hungary as EU countries with openly anti-immigrant governments standing in defiance EU freedom of movement police. And Mr Kurz claimed the credit for closing the Balkan migrant trail in 2016 that saw hundreds of thousands of refugees trek into western Europe.

World's youngest leader: Sebastian Kurz, 31, declares victory in Austria election Mon, October 16, 2017 Austrian election 2017: The Austrian People's Party emerged as the largest party in the National Council, winning 61 of the 183 seats Play slideshow EPA 1 of 22 Austrian Foreign Minister Sebastian Kurz, the leader and top candidate of the Austrian Peoples Party (OeVP) addresses his supporters during an OeVP's election party after the Austrian Federal Elections