Plans to expand an international airport near Berlin to create a new hub for the German capital hit a setback Thursday when a federal court upheld a complaint by residents in the area. The two-billion-euro ($2.6 billion) extension of Schönefeld Airport southeast of Berlin got the green light from state authorities in August. Underground construction work was to begin in January 2006 with the opening of the new Berlin Brandenburg International Airport slated for late 2010. But the ruling by the federal administrative court in the eastern city of Leipzig prevents any construction work that would be "irreversible" pending a full airing of residents' objections. Some of the nearly 4,000 plaintiffs would like to stop the project entirely. The court, which plans to make the final decision on the project in the first half of 2006, said it must weigh the needs of the region against concerns about noise pollution, security, water and wildlife protection. Harald Wolf, head of economic affairs for Berlin city-state, said the decision would allow preparatory work to begin nevertheless and would not necessarily produce delays for the project as a whole.