Serbian Prime Minister Aleksandar Vucic is due to visit Berlin Wednesday by invitation of Chancellor Angela Merkel for talks expected to focus on lagging reforms, slow normalization of relations with Kosovo and Belgrade's position on Ukraine, dpa reported. Vucic insisted he is travelling with high spirits to offer friendship that has not always bloomed between the European heavyweight and the Balkan country. Merkel invited Vucic as problems emerged on several fronts that are key to Serbia's EU membership bid.