SOFIA, Jan. 11 (Xinhua) -- Bulgaria's six-month rotating Presidency of the Council of the European Union (EU) was officially launched here on Thursday evening at a special ceremony attended by the highest local and EU officials.

"Europe is too big to be monolithic but too small to be divided," Bulgarian President Rumen Radev said at the ceremony held in the Ivan Vazov National Theatre.

Therefore, the motto of Bulgaria's EU Presidency is "United We Stand Strong", Radev said.

Bulgaria has taken up the Presidency in a difficult time, he said.

"I am convinced that when the problems affect everyone, the key is in realism and solidarity efforts," Radev said.

Donald Tusk, President of the European Council, said it is a good thing that one of the priorities of the Bulgarian presidency is the future of the Western Balkans.

"Who, if not you -- the descendants of Spartacus, the inheritors of the oldest European statehood, you, who never ever lost a flag in any battle -- would be better placed to rise to this important and exceptionally difficult task, that is to renew the European perspective for the whole of the region," Tusk said.

Bulgarian Prime Minister Boyko Borissov underlined that many questions would be asked and many answers given during the next six months on issues such as EU's cohesion policy, cyber security, common European defense, migration crisis, and providing a hope for EU membership to the peoples of the Western Balkans.

For his part, Jean-Claude Juncker, President of the European Commission, said that Bulgarian Presidency is taking place at a crucial moment when the EU has to carry out a number of initiatives in the interests of its citizens and shape its future.

Bulgarian Prime Minister Borissov could lead Europe and build bridges, Juncker said.

The President of the European Parliament Antonio Tajani, who also held a speech at the ceremony, said the motto of Bulgaria's EU Presidency "summarizes, in four simple words, our common endeavour for the coming six months: Together we must tackle the many challenges ahead of us and make Europe fit for the future. Together we must continue our reflection on how to improve our Union, to make it more efficient, more democratic and closer to our citizens, especially to the younger generations."

The ceremony, attended by a total of 780 guests, also featured performances of the anthems of Bulgaria and the EU, as well traditional Bulgarian songs and dances.

Meanwhile, near the building of the National Theatre, the visitors enjoyed an interactive exhibition portraying Bulgaria's long history, magnificent architectural monuments, natural beauty and iconic artistic masterpieces.