The eight parties announced they had reached a deal on the breakup of an electoral district in and around bilingual Brussels, an issue that had vexed politicians for almost half a century and was at the heart of the long standoff between the linguistic groups as they sought to change the constitution.

The parties said that negotiations on other issues, such as economic and social policy, would continue later yesterday.

“Our work is far from over, and we still need a lot of negotiations,’’ said the joint statement.

Still, after a government stalemate already considered by far a world record, news of the breakthrough was lauded by many as fundamental.

“It is a historic breakthrough. It is extremely important and positive,’’ said caretaker Prime Minister Yves Leterme.