MADRID — Spain’s acting prime minister Pedro Sánchez, seeking Parliament’s backing to form a government, pledged to resolve the Catalan dispute through dialogue as he received renewed support from separatists in the restive region.

As Mr. Sánchez set out his priorities on Saturday in an attempt to end several months of political gridlock, he assured lawmakers that neither Spain nor its constitution would break.

“What is going to break is the blockade of a progressive government democratically elected by the Spanish people,” Mr. Sánchez, the Socialist Party leader, told deputies in opening remarks as he kicked off several days of debates and votes in Parliament.

Earlier this week, Mr. Sánchez and Pablo Iglesias, the head of the far-left party Unidas Podemos, restated their intention to form the first coalition government in Spain’s recent history.