MADRID — Europe will be unable to afford its extensive social programs without economic change, the European Union’s new permanent president, Herman Van Rompuy, warned Friday, supporting calls for sanctions against countries that fail to honor pledges to reform their economies.

At a news conference marking the start of Spain’s presidency of the E.U., Mr. Van Rompuy shared the spotlight with the Spanish prime minister, José Luis Rodriguez Zapatero, and with the president of the European Commission, José Manuel Barroso. They went out of their way to resemble the “Three Amigos,” but the crowded stage highlighted the difficulty the bloc is having streamlining its leadership.

The E.U.’s six-month rotating presidency was supposed to be scaled back by the recently enacted Lisbon Treaty, which created Mr. Van Rompuy’s job. But on Thursday Mr. Zapatero set the political agenda by calling for a new European economic reform plan, which is about to be drawn up, to be made binding on national governments.

On Friday, all three leaders agreed on the need for a more strictly enforced reform program — an idea that would need the support of all 27 governments and that will probably be viewed with suspicion in Germany and Britain.