PRISTINA, Sept 29 (Reuters) - The European Union"s chief executive urged Kosovo and Serbia on Wednesday to overcome a mounting border dispute and recommit to mediated talks in Brussels, saying that as a German national she understood the challenges of reconciliation after conflict. NATO troops stepped up patrols in Kosovo on Monday near border crossings which have been blocked by local Serbs angered by a ban on cars with Serbian licence plates entering the country, in the latest flare-up between the neighbours. read more "I know what it means to overcome disputes ... I come from a country that brought World War Two to the globe and that is responsible for the Holocaust," European Commission President Ursula von der Leyen said in Kosovo"s capital during a visit to the Balkan region ahead of an EU-Balkan summit on Oct. 6. Serbia, Kosovo, Bosnia-Herzegovina, Montenegro, Albania and North Macedonia all aspire to join the EU, but progress has stalled since an EU pledge in 2003 to admit them once they meet all the criteria. read more Kosovo declared independence in 2008, backed by the United States, Britain and most EU member states, but Serbia has never recognised that, blocking its recognition at the United Nations. Both Kosovo and Serbia, which is an official candidate for EU membership, must improve mutual relations if they want to join the bloc. Their negotiators head to Brussels this week for the latest round of EU-mediated talks. "I hope that they come with a strong mandate to negotiate. That"s the best way to resolve the problems and move forward. I am deeply convinced it is so important to de-escalate and go back to a dialogue that is constructive," von der Leyen said. "We want a future where Kosovo and all the Western Balkans are part of the European Union," she added. Despite strong Commission support for Balkan membership of the EU, the bloc"s 27 members are divided over the speed of "enlargement" and specifically whether to start accession talks with Albania and North Macedonia.