Jean-Claude Juncker is to head the group of 16 countries which use the euro until the summer of 2012, dpa quoted diplomats at a meeting of eurogroup finance chiefs in Brussels as saying today. Juncker has headed the informal group since January 2005. Under the European Union's Lisbon Treaty, which came into force in December, the body takes on formal status with a president who serves for two and a half years. Finance ministers from the 16 countries which use the EU's single currency approved his appointment unanimously, diplomats said. Juncker is the EU's longest-serving premier, having headed the government of Luxembourg since 1995, and is also his country's treasury minister. Ahead of Monday's meeting, Juncker wrote to eurogroup ministers to present his candidacy formally. In the letter, he called for a single euro representation on world bodies such as the Group of 20 leading economies. "It is essential at this juncture to ensure that the euro area's interests are fully reflected in international discussions," he wrote. He also called for a dedicated secretariat to support the new president of the eurogroup in his work.