BRUSSELS — The European Union approved plans to tighten the rules governing the euro early Friday, and said it would seek more changes and a limited alteration to the bloc’s main treaty in December.

At a meeting in Brussels, the leaders of the 27-nation bloc approved a set of tougher budget rules, crafted by their finance ministers, which included new sanctions against eurozone states that fail to keep deficits and debt in check, and earlier warnings over asset bubbles and declining competitiveness.

Its declaration also said the union will consider ways to change its governing treaty in December to set up a permanent fund to help eurozone nations in times of crisis.

But moves by the German Chancellor, Angela Merkel, for a more radical alteration to the treaty were rebuffed, as the leaders emphasized a more limited and technical set of changes.